NL2026570B1 - Protective device for protecting a user of the device from inhaling air-borne pathogens from ambient air - Google Patents

Abstract

Protective device for protecting a user of the device from inhaling air-borne pathogens from ambient air, the protective device comprising: - a head-fitting piece that is configured to be positioned in a fixed position on the head of the user when the protective device is in use, which head-fitting piece is provided with a ventilation system and a facial cover; - the ventilation system comprises an air filter unit having a filter inlet for ambient air, a filter, and a filter outlet for purified air which is ambient air that has passed through the filter, wherein the ventilation system is configured to propel the purified air from the filter outlet towards the user in order to be inhaled; - the facial cover being configured to cover at least the mouth and nose of the user when the head-fitting piece is positioned in a fixed position on the head of the user, which facial cover is impermeable to air and in particular to air-borne pathogens, and the facial cover having transparent properties at least at a zone of the facial cover that covers the eyes of the user.

Description

Protective device for protecting a user of the device from inhaling air-borne pathogens from ambient air The invention is related to a device for protecting human individuals against exposure to undesired substances or organisms and minimizing the risk for developing hazards caused by the presence of these substances or organisms. In particular the device helps in protecting health care professionals against exposure to pathogenic microorganisms that origin from patients and minimizing the risk that they become infected during their work.

Field of the invention In certain situations, human individuals can become exposed to undesired substances such as hazardous chemicals or pathogenic bacteria or viruses. Exposure to these substances can result in significant harm or pathologies, and even in death of the exposed person. Unfortunately, people cannot always avoid arriving in such situations. For example, health care professionals like medical doctors, nurses, dentists and the like, need to investigate potentially infected patients for diagnosis or need to handle an infected patient for daily care or need to treat a patient. Also, outside the medical field individuals can experience high risks to become exposed to hazardous chemicals or microorganisms, for example during waste removal, during cleaning practices or when combatting fires. Other examples of such individuals are employees in research facilities where biological material is investigated, or operators during the manufacture of products which comprise hazardous material such as medication or biological material. During pandemic events or environmental accidents hazardous substances may be everywhere in contaminated areas. Typically, precautions are taken to prevent as much as possible exposure of the body of people that are at risk to become contaminated. For example, individuals are advised to wear protective clothing and/or operate within an environment with specially designed devices, which allows them to operate safely. Unfortunately, the protective clothing and devices, as disclosed in the art, demonstrate relevant shortcomings. These shortcomings depend on the type of protective item. If the protective device needs to offer more protection, the shortcomings are in general larger.

The degree of protection that a device offers against the transfer of a microbe (e.g. virus) from the environment to the human body is expressed as a value for the “biosafety level” (abbreviated as BSL). Protective clothing and - devices which meet the level of BSL3 or BSL4 are considered to be suitable for working safely in an environment which is contaminated with very hazardous and infective pathogenic viruses like SARSCoV2. BSL2 is considered to be suitable for work with viruses that cause HIV or hepatitis.

In order to secure 100% protection to an individual in such environment, it is typically aimed to cover 100% of all surfaces of the body that might become exposed, with a material which is impermeable to the hazardous substance or microorganism and not contaminated.

These surfaces include the trunk, face, eyes, hair, hands, nose and mouth.

Protecting devices includes cloths, helmets, shields, glasses, masks, gloves, et cetera.

It takes quite some time for an individual to cover him/herself completely with such material or put all protective devices in a perfect position.

Complete and robust positioning of the protecting devices is quite critical.

By wearing these protective materials and devices, free movement and breathing are often hindered.

Additional clothing, hair nets, protective glasses and mouth/nose masks are uncomfortable to wear; not only physically, e.g. by hindering movement or contact, but also mentally, for example because wearing creates a moist and warm feeling.

Non-transparent and closed masks placed over mouth and nose and helmets impair easy communication by the wearer with colleagues and patients.

In the medical field special attention needs to be paid to microorganisms that are excreted by the patient, which during diagnosis and communication is typically positioned in front of the wearer of the protective device.

For example by coughing, droplets which are contaminated with pathogenic microorganisms are propelled in the direction of the wearer through the air, which, without adequate precautions, can be inhaled by the health care professional or care giver.

The larger droplets comprise much more pathogens than aerosols, but may fall to the ground due to their mass, before they actually reach the health care professional.

Smaller particles and aerosols (which typically have a diameter of 0.2-2 micron), may reach the health care practitioner, especially when the room is insufficiently ventilated and the person remains for a longer time in such room.

When the patient coughs in the direction of the health care professional when he/she is at an insufficient distance from the source/ patient, as typically occurs during diagnosis and treatment, the directional movement towards the health care professional of larger droplets is considered to be the main source of contamination. The latter situation differs from most industrial situations, wherein hazardous fumes and volatile substances can be present everywhere in the proximate environment of the wearer. In order to minimize the risk to become ill, special attention needs to be paid to avoid contamination of the lungs of the wearer. The lungs have a very large surface compared to the skin, and therefore form a large port for entry of contaminants and microbes into the body. Pulmonary epithelial cells are also useful targets for viruses while these express on their surfaces those proteins that are required for a virus to attach to that tissue and subsequently infect the body. Infection of and damage to the lungs is also hazardous while proper lung function is critical to general health, while it provides the oxygen to allow proper function of most human cells. The lungs are also a vulnerable tissue, while it consists of soft tissue which is sensitive to damage of physical and chemical nature.

The gut forms another critical point of entry for pathogenic and hazardous substances into the body due to its large surface area and expression of suitable proteins on the surface of gut cells. Note that phlegm and sputum from the lungs may be swallowed and viruses therein can subsequently reach the intestine.

In order to protect the lungs and gut, devices have been developed which cover nose and mouth in an airtight manner. Wearing of these devices creates a space before the mouth and nose that is completely separated from the environment and filled with non-contaminated or sterile air which is suitable for inhalation. Air flow and breathing is possible through physical openings that are made in the device which allow passage of air. These openings are equipped with filters which form a barrier for the contaminants and/or microorganisms present in the environment but give free way to inhaled or exhaled air.

Many protective devices have been disclosed in the art, each having their own problems. Some prior art devices are mentioned and discussed in the section about the background in this patent application. Below are some general problems with prior art solutions described. For example so called “gas masks” have been developed, which fully cover the face of the user and have an advanced filtering system, consisting of several units, together suited for cleaning inhaled environmental air, e.g. by filtering or absorption of all kinds of hazardous substances. Though very helpful in industry and for specific military operations,

these devices are not convenient to use in daily practice in the medical field. Potential reasons are the problematic communication with other people, its inconvenience in use, and the creation of feelings of anxiety and fear in the patient. Gas masks which are equipped with electronic communication equipment, like a combination of microphone, amplifier, sender and a loudspeaker/ ear plugs, makes the mask complicated in use. At present also powered air purifying respirators are commercially available. Typically, these devices consist of 1/ a helmet which fully covers the head or a face shield or, 2/ a pump/battery/filter combination, and 3/ tubing, which tightly connects the helmet with the pump-filter combination. The air pump/fan is typically carried on the back of the user and the connecting tubing is therefore long. The powered pump blows air through a suitable filter system into the tubing to the helmet, thus allowing the user to inhale clean sterile air.

This kind of equipment is also rarely used by medical practitioners for protecting themselves against infection, due to a variety of reasons related for example to its size and inconvenience during use. Typically a conventional helmet completely covers the head, neck and face and hinders free hearing of speech and other sounds that the user desires to hear, which can be important, especially in the medical field. Another problem with powered respirators in closed systems is that these respirators supply excess air to the helmet for safety reasons. This can create overpressure in the zone around mouth and nose, which may hinder exhalation, and, on the longer term, tiredness and stress for the user.

Also, some systems have a noisy system for the outflow of air to the environment which mandates covering of the ears, which on its turn hinders communication.

Disadvantages of the use of continuous positive airway pressure (CPAP) have been summarized by Resmed in 1997. CPAP systems are typically used by persons suffering from sleep apnea.

The powered air purifying respirator according the invention is an_gpen system, so with free space between nose/mouth and the environment, which allows passage of air. Open systems have the general disadvantage that when the user inhales strongly in a short time, and the amount of purified air that is supplied by the pump/ fan is not sufficient to provide the desired air volume, ambient (non-purified) air is inhaled. In order to avoid this typically the volume of supplied purified air per time unit is increased. However, this makes the system and creates a dry mouth or cools the face too much, or gives un unpleasant feeling on those spots where the air jets approach the face on special spots, especially when the system is used for longer periods. The design of prior art open respirators not always prevents itching or allows scratching. Removal and clean storage of the device should be easy to do.

5 Apart from the above-mentioned advanced systems also more simple protective devices are available, for example face shields. These prevent that large droplets in the air, as exhaled by patients or as caused for other reasons, can directly contact the face of the health care professional or care giver. Advanced and large face shields can provide more than 96% protection against virus transmission, when the virus predominantly is transmitted from one person to another by means of large droplets (Perencevich, et al, JAMA 2020). Often the face shield is carried in combination with a mouth/ nose mask, to provide additional protection, e.g. against exposure to hazardous aerosols. Larger face shields can under certain circumstances like during cold temperatures, have the disadvantage that humid (e.g. exhaled) air condenses on the shield thus creating a fogged view. Sometimes the dimensions of the face shield don't allow wearing glasses which are needed due to vision problems of the wearer. Face shields can become dirty at the inside and outside. In order to allow one-time use, they often get simplified designs that can be manufactured at low cost.

Systems wherein the user's own force (for respiration) is used for the passage of ambient air through a filtering unit, include masks that just cover mouth and nose of the user. Such masks are in most cases non-transparent to light, except Clearmask®. Typically the filtering unit is integrated in the mask. The choice of filter(s) determines what degree of protection is obtained; some filters protecting against inhalation of dust and larger particles in the air, others protecting the user against inhalation of droplets or aerosols, which comprise hazardous substances like viruses. A mouth/nose mask leaves eyes and other parts of the head open for contamination, which is why these masks are often carried in combination with eyeglasses and a hair net. When the user of the mask wants to pause the work, it is common to remove the mask from its position and discard it when it has been used for some hours.

Mouth/nose masks are uncomfortable to wear while accumulation of exhaled air behind the mask may be moist, smelly and warm. Such masks hinder free breathing and impair open communication with colleagues and patients by deformation of sound and hiding the mouth.

Masks which fully cover at least mouth and/or nose should fit tightly to the skin, in order to prevent that ambient air is inhaled. Typically, the masks are manufactured of a flexible material which allows careful positioning of the border or edge of the mask against the skin. Correct positioning is critical for obtaining BSL3 or BSL4 protection and displacement during use should be avoided. Unfortunately little possibilities exist for the user to check whether the mask is securely positioned or has been moved during use. This also applies to the use of other protective devices like protecting eyeglasses. During use and storage masks need to be handled with care in order to prevent puncture of or damage to the protective layers or filter.

Inthe art some types of filtering units are disclosed which apply one or more advanced technologies to create a proper barrier to the small sized virus particles. These technologies may include systems for chemical sterilization of the inhaled air. Manufacturing of such caps requires advanced technologies in order to guarantee 100% protecting properties. This applies to the manufacturing process of sterile filters, and optionally sterilizing devices, 100% airtight sealing of all components in the mask to ensure that all inhaled air passes the filter, and also to the quality control procedures that need to be applied to ensure that the masks meet the desired specifications. Regeneration of such complicated filters is either complicated or impossible in daily practice.

While replacement of filters creates risks for air leakage, most of these masks are single-use items. This creates in daily practice a high volume of waste. Because the filters can comprise pathogenic microorganisms after use, handling and disposal needs to occur with caution in order to avoid contamination of the environment and other persons. Waste handling including its packaging, logistics and destruction is therefore complex and expensive. The amount of waste is further increased by the need to use advanced packaging materials for keeping the devices sterile after manufacture, e.g. during storage until use.

The characteristic that protective materials are only suited for single use also puts high demands on logistics for manufacture and distribution of the devices to all medical care centers which need the protective material. These centers can be located all over the world, as demonstrated during the current covid19 pandemic, while the manufacturing occurs in other countries. During sudden, unexpected or large outbreaks of infectious diseases available logistic requirements might become insufficient.

The new protective system does demonstrate much less of the afore-mentioned problems as exist with the use of the protective devices as disclosed in the art. It allows the user to apply all operational activities as required, in particular medical activities that are needed for examination and treatment of the patient, which include for example the use of a stethoscope. The device allows free movement of the head and a clear sight, e.g. the materials used by the wearer, on the patient and on colleagues that are around. It allows more effective communication with others, in terms of visibility of facial emotions and allowing speaking and hearing of low-distorted sounds. The device is comfortable to wear, easy to apply (e.g. on the head), easy in use (e.g. switch on and off), easy to store or remove and put aside for example during interruptions in the use, like during a pause in work. Positioning of the system is much less critical than prior art systems and any contamination is not critical due to the outward directed air currents behind the transparent first part. Wearing doesn’t induce itching in the face, by making no contact to it.

Wearing of the new device also allows wearing of some additional protective tools, like a coat, mouth mask or eye glasses, as considered necessary by the medical practitioner, but decreases significantly the need for wearing those tools. Background of the invention Inthe prior art, devices have been described to improve respiration of individuals in an environment which forms a threat to health due to the risk to become infected by microorganisms or become contaminated with hazardous volatile material. Typically the design thereof addresses specific needs that result from the conditions in which the systems are used. However, the prior art devices have certain disadvantages and therefore a general need exists to further improve these devices.

For example in US 3,822,698 a helmet or hat is disclosed which is especially designed to avoid that dust and ubiquitously prevalent allergens are inhaled. The helmet is equipped with a built-in powered air blower and air filtering system, which removes contaminants from the surrounding air. The blower delivers purified air to the area that is present between the wearers face and a visor and transparent face shield that is fitted to the vigor. This air can be inhaled through nose or mouth and excess air and exhaled air escapes through an opening between the bottom of the mask and the wearer’s chin. This large local air flow propels exhaled air, which is potentially contaminated with viruses or bacteria, over a relatively large distance in the direction of a person that opposite to the user (of the system). The face shield is relatively short which mandates the blower to supply a large excess of air to the breathing zone, in order to prevent that during large inhalations the user also inhales ambient air through this opening between chin and shield. A large and fast air current dries out mucous tissues, like those in the eyes, nose, mouth and throat. Filtration of ambient air is achieved by use of a large surface filtering textile located in the helmet, which is not easy to replace or clean. Filters for dust are not suitable for filtering viruses from the air. The respirator helmet is not covering most of the chin, neck or ears, and also does not create a protective zone around the head thus mandating the wearing of additional protective devices when the wearers needs protection from hazardous gases or microorganisms.

These problems are much less when a person uses the protective system according the invention.

The second problem is related to the low convenience and comfortability when wearing the system, as caused by the air intake system and helmet. The air intake system receives a gaseous medium from a gaseous supply system or ambient air into the helmet and directs it towards the breathing zone. The gaseous supply system can be a cylinder bank, compressor, blower or air purification assembly, which is carried on the back and whose air outlet is connected with a hose to the helmet. Movement of the head is facilitated by making this connector flexible. The helmet is relatively heavy to wear, because of the rail system with wheels, which is designed to function robustly in a dusty environment, but also because of its dimensions and frame design, and because of the large shield.

The third problem is related to the module with one or more channels that is clamped in the interior of the helmet. This module directs the air that enters the helmet through the hose, to “an end on a platform in the front part of the helmet”, but it remains unclear how the air that leaves the platform precisely distributes over the face during use. It seems that the purified air leaves the platform near the forehead, and flows along the eyes and past the face to a chin frame with some apertures or to a space between a shield and body, where it leaves the breathing zone. The protective system according the invention crates a defined protective air current over the face, which creates a safe breathing zone around the nose and mouth in and outside the face shield.

The fourth problem is related to the optional additional small motor which can be built in the helmet. This motor is powered by the air currents under the helmet and serves as a small generator for powering warning LEDs which reflect the magnitude of the air flow in the helmet. This motor apparently can also “draw in ambient air into the helmet into an aperture” that is located at the rear side of the helmet, and “through a filter and into the channel to the breathing zone”. The channel module is clamped in the helmet to facilitate removal and cleaning, “which is desirable”. Though such system may be useful to remove dust from air for inhalation, this system does not seem useful for protection of the user against inhalation of microorganisms, like viruses.

The fifth problem is related to the large hood or shield that can be fitted to the chin frame and covers breast, neck, shoulders and back. The space between shield and body and the space between visor and face create a relatively closed breathing zone, which is separated from the environment. Exhaled - and excess air can leave the breathing zone either through the space between neck and shield/ gather, or, when the shield is attached to the neck, by means of specific apertures that are made in the chin frame for exhalation through relief valves in the air supply system.

Terminology In the context of this patent application the following terms are used: An air supply system — also referred to as a filter unit - is made of one or more devices which together move purified ambient air to an outlet, which can be connected to the air guiding system. The air supply system comprises a little pump or motorized fan or - propeller, a filtering system for removing the hazardous substances from ambient air, and a powering system, which powers the motor of the pump or fan.

The air guiding system — also referred to as a duct system - is a set of one or more interconnected ducts, conduits, hoses or tubes which allow the transport of purified air from the outlet of the air supply unit to the one or more places between the system and the body, face or skull of the wearer.

The ventilation system is the combination of the filter unit and the duct system together. The filtering system — also referred to as a filter - is the device which forms a barrier to hazardous substances that are present in the air that is blown by the fan or pump through the device. The device can comprise several parts. For example it can comprise a removable cassette of filters which fit in the housing of the device.

The second part of the protective system — also referred to as the head-fitting piece - are the parts which together allow positioning of the air supply system on the head. It is a means to position the system on or to the head, but can also comprise several other functional devices.

For example it can also comprise a part which largely covers the head, thus replacing conventional helmets or hair nets. It can comprise some or all of the air guiding system. It can comprise a chin frame. It can comprise means for attaching a flexible third part to or hinges to attach the first part to. The third part — also referred to as a protective hood - can comprise one or more sheets that fall down on the shoulders or over the neck, thus protecting these body parts from direct contamination.

Sterile air is air from which microorganisms have been removed to the level of BSL3.

Air-borne pathogens are substances that could harm a human being. These include dust, small particles, many chemicals and toxins in volatile-, liquid- or solid form, and pathogenic microorganisms, to which for example many species of bacteria and viruses belong. General description of the invention In order to solve the problems as occur during the use of traditional devices for the protection of the user against exposure of the respiratory system and face to hazardous substances and micro-organisms, a protective device has been invented according to appended claim 1 which defines: a protective device for protecting a user of the device from inhaling air-borne pathogens from ambient air, the protective device comprising: - a head-fitting piece that is configured to be positioned in a fixed position on the head of the user when the protective device is in use, which head-fitting piece is provided with a ventilation system and a facial cover; - the ventilation system comprising an air filter unit having a filter inlet for ambient air, a filter, and a filter outlet for purified air which is ambient air that has passed through the filter, wherein the ventilation system is configured to propel the purified air from the filter outlet towards the user in order to be inhaled; - the facial cover being configured to cover at least the mouth and nose of the user when the head-fitting piece is positioned in a fixed position on the head of the user, which facial cover is impermeable to air and in particular to air- borne pathogens, and the facial cover having transparent properties at least at a zone of the facial cover that covers the eyes of the user; wherein, when the protective device is in use, the facial cover creates an air pocket between the face of the user and the facial cover, from which air pocket the user inhales air and into which air pocket the user exhales air; which air pocket is in fluid communication with ambient air at one or more peripheral sections of the facial cover; wherein the ventilation system contains a duct system connected to the filter outlet and through which, when the protective device is in use, purified air from the filter outlet is led towards at least two exit openings of the duct system which exit openings are in direct, fluid communication with the air pocket, so that purified air is introduced in the air pocket.

The invention establishes a continuous flow of purified air which is led into the air pocket, thereby preventing that the user is inhaling ambient air that is not purified.

The at least two exit openings of the duct system allow for an even, or homogeneous spreading of purified air that is introduced in the air pocket, when the device is in use, and the user breathes from the air pocket.

In addition, the multiple exit openings can be positioned at locations that do not irritate the user, in particular the user’s skin.

Furthermore, the use of multiple exit openings in the duct system allows for a relatively slow outflow of purified air into the air pocket from each individual exit opening, which is more effective in creating an air pocket being continuously filled with a homogeneous amount of purified air, because less turbulences will occur at a slow outflow.

Additionally, it may also result in the total amount of purified air that is required to be introduced per second into the air pocket, is kept relatively low.

Dependent on the specific design of the protective device, it may be preferable that the duct system comprises more than two exit openings, e.g. three, four, five or six. Even higher numbers of exit openings are contemplated by the invention. The facial cover of the protective device may be dimensioned to cover the entire face of the user, or alternatively be designed as a mouth cap as defined in respective claims 2 and 3. Further preferred embodiments of the invention are defined by the appended dependent claims 4-12.

In particular, various specific locations of the exit openings of the duct system are preferred within the realm of the invention. Furthermore, it is preferred that the facial cover has different peripheral sections which are either in abutting contact with the face of the user, or located at a distance from the user's face. As such, the specific flow of purified air can be regulated both in terms of homogeneity, and in terms of required air flow.

A protective hood, which comprises a protective device according to the invention, is also contemplated as another embodiment of the invention as defined in claim

13.

More specifically the air guiding system comprises one or more ducts, conduits and/or tubes which have more than one opening for allowing the purified air to leave the guiding system on the specified places. These places have been selected in such a way that during use the space between the facial cover and the face becomes filled with purified air, thus preventing that ambient air will be inhaled during use. Excess air leaves the zone between the first part and the face or head through the large open space between face and facial cover, so away from nose and mouth where a small overpressure was created by the air supply.

This zone of purified air behind and closely besides the facial cover, especially around nose and mouth is called the breathing zone or air pocket. The purified air is supplied in a way that it does not dry out the eyes as much as prior art systems do, and also does not form a jet on the skin. This, together with the relatively little noise of the moving air makes it a comfortable system to wear and use.

The air guiding system can be integrated in the second part or ventilation system.

The second part which positions the air supply unit to or on the head and the air guiding system can thus form a module which can be worn on the head and be used in combination with commercially available face shields. In a different embodiment the air guiding system is partly integrated in the first part, because of a system of hollow conduits which are molded in the transparent first part or face shield during its manufacture or are glued to the sites of the first part.

By bringing the face shield in the use-position, so before nose and mouth, connects these conduits to the other conduits present in the second part. Despite the fact that the protective system according the invention is an open system, with theoretical free movement of gases, including ambient gases, through the openings between system and body, the system is much more safe than conventional non-ventilated face shields, as used in the medical field, because of the overpressure of purified air in the breathing zone. The preferred bended shape of the first part, which causes that the sides approach the face, decreases the risk that ambient air enters the breathing zone. This makes that the system is useful when walking in a city or during travelling in open air, where the risk for exposure to a virus is generally low, but also during medical examination of potentially infected patients and during nursing and health care of patients. When more protection is needed, for example when a patient is known to be infected with a pathogenic microorganism, additional technical features can be added to the basic system, as elaborated in the section about the detailed description of the invention. The spread of air that is exhaled by the user over large distances into the environment has been minimized, because the surface of the openings along the first part is so large that the velocity of the moving purified air is relatively low. This decreases the risk that a health care professional who would be infected with whatever microorganism will infect patients that will be examined by the same person, compared to prior art systems which guide exhaled air through relatively narrow openings. When more protection is needed, or when the protective system needs to be used in an industrial environment where dust and protection against mechanical impacts is required, the basic system can be equipped with additional technical features, thus forming one system in which several functions are integrated. The complete system also decreases the need for wearing/using additional protective devices, such as a hairnet, and protective eyeglasses. Nevertheless it allows wearing of additional devices such as glasses, hair nets and the like, is considered useful by the wearer.

The protective system according the invention can therefore be given a form which complies with the requirements for reaching a proper biological safety limit, which people in the art aim to achieve by wearing a combination of face shields, mouth and nose mask, eyeglasses, hairnets, helmets and protective gowns, but it is more convenient in use, and allows better face to face communication.

Use of the system results in less waste.

In preferred embodiments, the system according the invention comprises one or more of the technical features, as specified in the next section about the details of the invention.

These features can be applied, either independently or dependently from each other.

The various embodiments of the protective system according the invention allows the wearer to operate in a safe and convenient way in an area that is contaminated with hazardous substances.

The system provides sufficient amounts of purified air during normal daily activities at work but also has a large buffering volume for additional purified air which can be inhaled in unexpected circumstances.

Filtering of the air is done according to the standards needed to create the proper biological safety level.

The filtering system that is used is preferably a so-called cartridge system that can be easily replaced and/or cleaned.

The latter minimizes waste.

Purified air is supplied to the area around nose and mouth in a pleasant way to the user, so devoid of air jets which project on the skin and without drying-out mucous layers of eyes, nostrils and mouth.

The flow of fresh purified air from the air supply unit along the cranial surfaces prevents accumulation of heat and moisture between the protective system and the head; so prevents condensation of moist exhaled air within the system and keeps the facial shield clean and transparent.

As mentioned before the exhaled and excess air leaves the protective system between user and the source of hazardous substances, and thus creates a zone of purified air around the body of the wearer of the which can protect the body of the wearer against contamination.

This further decreases the need for wearing additional protective devices for achieving BSL-2. Wearing of the system allows clear view on other persons and environment, awareness of the facial expressions of the user by the patient and the use of eyeglasses or a stethoscope for examination of a patient.

In one embodiment of the invention the air guiding system releases purified air between the head-covering part of the second part and the skull which removes heat from the skull. The release of purified air between the first part and the face of the user keeps the quality of the inhaled air high, compared to wearing a mouth/nose mask, and minimizes inhalation of air that was exhaled shortly before.

The air guiding system projects the air in a defined - and well distributed way along the face to the zone around nose and mouth. The air flows predominantly in a laminar way along most of the surface of the face, which is comfortable and decreases the noise that normally comes with large and turbulent air flows.

The overpressure of the purified air in the breathing zone compared to atmospheric pressure is low, thus not hindering exhalation by the user. Detailed description of the invention When in use, the protective device has open connections with the environment through which air can pass. The overpressure against atmospheric pressure, as created by the active air supply unit in the space between the head of the user and the system or in the breathing zone, makes that the net direction of the air flow through the openings is away from the head of the user. In this way it is avoided that contaminated air enters through these opening and can be inhaled or can come in contact with the face or head. In most situations in the medical field, in particular during medical examination of patients and care of home patients this offers enhanced protection compared to wearing face shields as such, or wearing non-medical mouth masks. In order to achieve this outward directed flow of air it is preferred that the average overpressure in the breathing zone is between 0.01 to 0.2 atm over ambient atmospheric pressure, and more preferably 0.015 to 0.1 atm. In order to achieve this average level of overpressure, the system is designed that the venting openings between body and system, and optionally in the first — or second parts of the system itself, which create some resistance to the outward directed flow of air that was blown into the breathing zone by the air supply system. lt is preferred that the air supply unit has a capacity of about 4 to 100, preferably 5 to 40 and most preferably 6 to 24 liter per minute, in order to have sufficient capacity for safety in the design of the invented protective system. These flow rates are relatively low compared to those in the art and don't dry out mucous membranes or tissues like the eyes, nose and mouth. The resistance created by the venting openings also prevents that ambient air is entering the breathing zone, when the user inhales within a very short period a large volume of air, which exceeds the amount of air that is continuously supplied by the air supply unit. During this brief period the excess air that is needed is provided by the air present in the space between the system and the body, which forms a buffering volume of non-contaminated air. When inhalation would tend to result in under-pressure in the breathing zone compared to ambient air pressure the venting openings in the system can be equipped with one-way valves; or, alternatively, when the system is equipped with a flexible third part which loosely covers the space between the second — or first part and the body, the potential under-pressure or vacuum in the breathing zone will make that ambient air pushes the flexible parts, such as a sheet, against the body, thus temporarily increasing resistance to air which would flow inwards the breathing zone following the pressure gradient, until the moment that air supply rate meets inhalation rate.

The relatively large and optically transparent first part not only allows a substantial view on the face of the wearer, thus facilitating effective face-to-face communication, but also covers most of the chin, thus preventing that sudden inhalation through the mouth would result in inhalation of ambient potentially contaminated air. The face shield has a length that is longer than the distance between eye brows and chin of the wearer, so preferably longer than 14 cm, more preferable 15-26, most preferably 16-24 cm. Preferably the face shield has an optically transparent part that also has this length.

The air-guiding system according the invention with the ducts, conduits, tubes or hoses, releases the supplied purified air to outlets of the conduits at more than one place in the space between head and protective system. This results in a relatively slow movement of released air along the head. The general overpressure and the presence of several and/or large openings from the breathing zone to the outside world or optional third part allows venting of excess air and exhaled air through a large surface, which decreases air flow velocity. This decreases noise and/or creation of uncomfortable air currents on the skin, while still maintaining a large refreshment rate of air in the breathing zone and comfortable cooling of the face and head during use.

The absence of large local outward air currents is also safe to people in the environment, while the air that is exhaled by the user and might contain microorganisms, is not blown with great force in outward direction to people that are around. In a preferred embodiment at least part of the air is blown behind the first part between eyes and chin. This results in much less drying of mucous tissues like the eyes during use. In order to further improve the air flow along the face, in particular ensure a diffuse flow of air along the face, the invented system applies 2 technologies, either independent or in combination. In one embodiment where the porous end piece is absent, the number of outlets is increased. Preferably this number is more than six. In an alternative embodiment at least one the outlets of the air guiding system, is equipped with a porous end piece. This spreads the air that leaves these outlets into multiple jets and decreases the velocity of the air flow. Summarizing the benefits of the system, as described above, the preferred embodiments create a higher degree of protection compared to what is provided by face shields as known in the art, by blowing purified air behind the shield at specific places. This is done to create a maximal effect and offer most convenience for the wearer during use. The spread of air that is exhaled by the user over large distances into the environment has been minimized, which decreases the risk to contaminate people in the close environment when the wearer would be infected. it is convenient and comfortable in use, compared to mouth masks and combinations of such masks with eyeglasses and hairnet, and allows better face to face communication, with people around. Use of the system results in less waste. When more protection is needed or when the protective system needs to be used in an industrial environment where dust and protection against mechanical impacts is required, optionally additional technical features can be applied on the basic system, dependent on the degree of safety that is aimed for. The complete system decreases the need for wearing/using additional protective devices, such as a hairnet, and protective eyeglasses.

In preferred embodiments, the system according the invention comprises one or more of the following technical features, which can, either independently or dependently from each other, be applied to the basic embodiment of the protective system, dependent on the degree of protection which the wearer desires:

- a protective system wherein the purified air is exclusively supplied by the one or more air supply units that are positioned in or on the second part.

The absence of air supply systems positioned on either the hips, belly or back, makes that no lengthy hose or tube is needed for guiding the purified air from pump to the head, which typically hinders physical movements of the wearer or people around.

A second part without a long hose is relatively easy to apply on the head.

In the medical field it is also important to avoid to frighten the patient with large robot-like protective devices. - a system wherein the air supply system that is positioned in or on the second part is an electrically powered air pump, blower or fan.

This way of supply of energy allows safe and robust construction and manufacture of a system that is flexible and convenient in use.

It can be used where mobility of the wearer is required.

The energy supply can be done by for example batteries, which can for example be for single use or be rechargeable when empty.

The batteries might also be powered by the electricity provided by light sensitive cells, present on the system. - a first part, which is a predominantly optically transparent face shield having a substantially flat - or curved form in front of the face.

This allows the user to have an undistorted and wide view on the environment like a patient, and allows people that are around to observe the face of the wearer, including the mouth and facial expressions, thus allowing face to face communication.

The transparency of the face shield also allows a clear undistorted sight on the wearer's hands during precision work or on the patients face, writing or reading documents. - a first part which during wearing before the face does not touch the cheeks of the wearer.

This leaves room for air to leave the breathing zone along the cheeks and face; - a second part, which covers a major part of the skull or hair, like a hard cover helmet or - cap, and is attached to the face shield in a way, which allows it to have at least two positions relative to the second part, and is equipped with an air supply unit.

In one embodiment the head-covering part of the second part is covered with a unit of light sensitive cells which for example can charge the batteries during full daylight or when working under lamps. - a second part which comprises one or more hinges, which are attached to the first part and allow its movement from the stable downward position before the face to a stable second position away from the face and if desired back again in front of the face. The hinge can for example be a single one located on the second part near the forehead, or for example be two hinges, wherein one hinge is positioned on the second part near one temple and the other hinge to the second part near the other temple. This turning system has a low mass, is easily cleanable and does not require as much maintenance as a rail-wheel system, during medical practice. A low mass of the system minimizes fatigue during wearing.

- a second part which fits on the head in a way that a zone is formed between the head and second part which is separate from the environment, and which comprises an air supply unit that blows the air through a filtering unit before it is delivered to the space between head or face and the system, thus preventing that the conduits, tubes or hoses of the air guiding unit become dirty and need frequent cleaning.

- a second part which comprises a covering part of hard light non-porous material in a form that covers the head, and has attached to its interior at least three spacers of soft deformable material, like a dry foam, which allow positioning of the covering part on the head but leaving a space between skull and the covering part. This space can be filled with hair and be used for ventilation purposes.

- In an alternative embodiment the second part comprises a hard covering part and some straps or belts that are attached to the covering part. The belts or straps can be bound to the head, thus positioning also the covering part on the head.

- a second part, which comprises a module, which filters microorganisms from ambient air to at least the BSL4 standard and preferably is easily replaceable. The filters preferably are placed in a replaceable cartridge which fits in an airtight way within a holder that is localized between the blower and an outlet to which the air guiding system through which the purified air is transported to the breathing zone. - an additional separate third part, which is made of one or more parts of flexible material that is substantially impermeable to hazardous substances or microorganisms, and can be removably fastened to the first part and/or second part, in order to cover parts of the head, face, neck and/or shoulders that are left uncovered by wearing the first and second part of the system and might become exposed to hazardous substances or microorganisms.

- a third part which during use, is connected on one side to the second part or to the face shield in a substantially airtight manner and is on the other side flexibly connected to or following the shape of the head or neck or shoulders of the wearer, thus forming a space between the body and the system that can be filled with purified air and exhaled air of the user. The third part also forms a barrier to microorganisms that have been exhaled by the user and avoids that these are directly propelled to people that are close to the user.

- A set of air-guiding ducts and tubes which directs part of the flow of purified air from the pump to several locations between head and the first — or second part, including at least one position between eyes and chin, thus preventing discomfort for the wearer such as local cooling or drying of eyes, - A second part which covers most of the hair but not fully the ears and is manufactured from a material that is impermeable to hazardous substances that are present in the environment close to the wearer.

- A system whose hard and impermeable materials, like plastics or metals, have been coated with a material which facilitates cleaning and hinders attachment of microorganisms to the surface.

- A second part which comprises a part that is impermeable to hazardous substances, including microorganisms, and largely covers the head, and has some extensions or spacers, or a rim of elastic - or soft deformable material, which allow firm positioning of this covering part on the head, leaving a space of at least 4 mm between most of the skull and the covering part and preferably 10-50 mm. This space is sufficient for holding the hair of the wearer, for ventilation purposes and/or for containing the air guiding system, i.e. the ducts, conduits, tubes or hoses for guiding purified air to special places between face and the first part. Blowing air in this space creates a flow of purified air under the covering which results in some cooling effect, which is experience as comfortable during longer term use of the system or in hot working conditions. This air origins from the air supply pump and is preferably only a part of the total output of the air supply unit, the remainder flowing to the space between face and shield or elsewhere to create a gentle and safe supply of purified air in the breathing zone.

- A second part which consists of a set of belts or elastic straps, which can be fastened to the head but doesn’t completely cover it; the set allowing fastening to the head of the air supply pump, filter unit, batteries and the air guiding system which guides the purified air to the space between the face and first part, and/or allowing fastening of a flexible third part which covers most of the head, neck or shoulders but not the face shield.

- A third part which comprises several parts, each removably fastened to the covering part of the second part, or to the face shield but not completely to each other, which parts together form a barrier to ambient microorganisms to contact head, neck, or shoulders by the impermeability of the material and the overlap of the different parts, characterized that near the ears two parts approach each other and the space between them can be widened manually to form a gap which allows positioning of a stethoscope, a headset or plugs in the ears. - A third part that gathers excess — and/or exhaled air, thus creating a reservoir of purified air around the body of the wearer that can be accessed for inhalation and/or protects the body against contamination by ambient microorganisms, due to the net flow of purified air away from the body - An air guiding system which distributes the flow of purified air from the pump to the skull or face, thus making sure that the purified air flows in a gentle and diffuse way along the head and/or face to the nose/mouth region. The ducts, tubes or hoses as used in the guiding system have outlets which keep the velocity of the leaving air relatively low and the outlets point in a direction away from the skin of the wearer, this avoiding that a jet of air directly hits the skin. In particular the positioning of the outlets is away from the eyes. It is preferred that over 40% of the output of the pump flows in a substantially laminar way along the skin of the face. A major part of the purified air is guided past the eyes before it enter the space around the nose and mouth. The air guiding system can be a combination of one or more connected ducts, tubes and/or hoses as a separate entity which is fastened to the second and first parts where needed. This fastening can be done by methods known in the art such as gluing or clamping in preformed clips. The air guiding system can also be integrated fully or partially in the first part, i.e. the face shield and helmet. The latter can be done by molding the ducts during manufacturing of the face shield or helmet. - An air guiding system which guides the flow of purified air from the outlet of the pump to at least 4 outlet positions between face and shield. - A first part which is at least 3 cm away from the eyes of the wearer thus allowing the user to wear eyeglasses during use of the protective system

- A protective system which during wearing creates a volume of at least 600 ml, preferably 800 and 2400 ml, most preferably 1000 to 2200 ml between the body of the user and the inner surfaces of the sum of the first and optional third part. - A first part which is a face shield with openings at specific locations at the front of the face shield, thus further improving communication by speech. - A second part equipped with an air supply unit and electronic means for regulation of air blowing rate. This can be done by methods known in the art, such as remote control of pumping speed or by remote control of a flow regulating valve which is placed in the air conduiting line.

- One or more flexible sheets or garments as third part, which is or are connected on one side to the second part, the chin frame or air-guiding system, and on the other side fits loosely around the cheeks, jaw, neck and/or shoulders of the user. The length of the sheet is preferably sufficiently long to be able to touch the body of the user of the protective system when the sheet is attached to the second part, or frame or air guiding system.

- Preferably this flexible side of the sheet has a cord attached to it over a main part of its length, which allows some tightening and minimization of the space between the flexible side and the head, neck or parts thereof.

- A flexible third part has openings, which together allow that the air that flowed along the face of the user leaves the space around the head in a predefined way, which is comfortable to the user and creates a volume of cleaned air around the body of the user of the protective system.

- A second part having a frame that is connected to the part which covers the head and is shaped around the face to harbor the sites of the face shield in closed position and to allow attachment of parts of the flexible third part - A second part which is equipped with a head phone, microphone or other equipment needed for electronic communication with a patient or other people around or for listening music or news. The second part preferably comprises the system for supply of electricity, such as batteries, which can be rechargeable or replaceable. The batteries can provide the electricity for the air supply unit, the communication equipment or headset, and for optional warning signs, such as LED lights or audible signals.

- A second part equipped with a hollow chin frame which is part of the air conduit system for guiding purified air from the outlet of the air supply unit to the face, and which follows the contours of the jaw while connecting one side of the covering part near the temple or ear with the other side of the covering part near the other temple or ear, characterized in that the chin frame has more than one aperture at the inside. These apertures allow supply of purified air to the breathing zone. Preferably the chin frame is equipped with means to attach a flexible third part to, more preferable in a non-permanent way.

- A second part wherein the air supply unit is powered by a source of electricity which is positioned outside the second part. This allows the source of electricity to have more capacity or power and have a higher weight, but also decreases the weight of the second part. Preferably it is positioned on other parts of the body than the head, such as the back or shoulders, in order to facilitate the mobility of the user. This positioning can be done with suitable means known in the art, such as a belt. The electricity supply unit is connected to the blower or fan with a wire or cable for transfer of electricity.

When the protective system has to be useful for full protection to the level of BSL3 or 4, a preferred embodiment of the system comprises for example: - as first part a face shield, which is predominantly made of optically clear material and having dimensions which, when put in front of the face fully shield the face from droplets which are exhaled or sneezed by a person opposite of the wearer, - as second part a device, which covers most of the skull or hair (such as a helmet or a cap) and is attached to the face shield with a means which allows the face shield to have at least two positions relative to second part, and wherein the latter comprises a means to attach a powered air supply system in a fixed position on or close to the device, which filters and blows the purified air into the air guiding system, and - a third part connected on one side to the second part in a substantially airtight manner and the other side flexibly connected to or following the shape of the head and/or neck.

Additional technical features have been described elsewhere in this patent application and include measures to allow regulation of the flow of purified air from the pump to the skull or face, and the presence of replaceable filter cartridges or cassettes and the cleanability of the filters.

These optional additional features also include the use of a flexible sheet as third part, which is connected on one side to the second part and the other side fits nicely around the cheeks and chin of the user. Optionally this flexible side has a cord connected to it over a main part of its length, which allows minimization of the space between the flexible side and the head or parts thereof. Optionally the flexible third part has openings, which together allow that the air that flowed along the face of the user leaves the space around the head in a predefined way, which is comfortable to the user and creates a volume of cleaned air around the body of the user of the protective system.

These optional features also include a second part which is a face shield with openings at specific locations at the front of the face shield, thus further improving communication by speech. These opening are for example covered with a lamella which allows free movement of air in one direction, outward the face shield, but strongly restricts movement from outside inwards the breathing zone.

These optional features also include the presence of a tubing system, which distributes the cleaned air from the outlet of the pump to at least two, but preferably 4 or more positions between face and shield.

Most currently commercially available face shields consist of a optically transparent solid plate, film or sheet of uniform thickness, mostly made of some transparent plastic material, like poly(methylacrylate (PMMA, plexiglass or Perspex) or polycarbonate. The material is a thermoplastic polymer and can for example be welded in various forms. One face shield that appears useful is one with a part of the air guiding system welded into the face shield at the sides or glued to these places. This part of the air guidance system connects to the other part of the air guiding system, when the face shield is in the use-position, i.e. the stable position before the eyes. The ducts of the air guiding system have openings which distribute the air along the face. The presence of the air guiding system in the face shield can be considered as a hollow deformation, while the face shield doesn’t have a uniform thickness anymore.

A useful embodiment of the invention is therefore: a/ an optically transparent face shield, wherein the shield has been equipped with one or more hollow deformations, conduits, ducts or tubes, which guide the purified air, which is propelled by the air supply system, to the space between shield and the face along the surface of the face in a predetermined way in at least 2 and preferably 3 to 100 positions and more preferably 6-80 positions, and b/ a second part, which is worn on the head as described before, wherein the air supply system comprises an air-purification unit, a battery, and an electrically powered air pump or ventilator/fan. Optionally the ventilator is a fan which blows the air into a tubing system. The tubing system comprises one or more parts which allow connection of the outlet of the fan to the entrance opening of the filtering unit, the filtering unit itself, and one or more parts which connect the outlet of the filter unit to outlet openings close to the skull or close to the face of the user of the system. The part of the air guiding system between the filter unit and the outlets preferably has no leakage to the outside environment. More preferably all parts of the tubing system are connected to each other in an air-tight manner.

The air guiding system conduits the air to outlets which have fixed positions between the face shield and face. Optionally some of the outlets are positioned to blow air between helmet and skull. The latter helps cooling of the skull during wearing the helmet.

Optionally the fan has a diameter of at least 4 cm, and preferably >6 cm, having a minimal output of at least 0.24 preferably 0.3 to 6 m3 per hour. Suitable supply pumps, ventilators or fans, are powered with a battery providing a voltage of 9 V or more, preferably about 12 V. Preferably the battery is rechargeable.

Optionally the purification system can comprise absorbents, grids, and mechanical or electrostatic filters, as desirable by the specific hazards to which the wearer can be exposed. Preferably the purification occurs by a set of filters which are mounted in a construction which is physically robust and fixes the filters in a position which ensures flow of air through all filters and full functionality of all filters. This set of filters, including the housing wherein they are placed is called the filtering unit. This filtering unit Preferably this filtering unit can be removed from the air supply system and exchanged for a new one. Such removable filtering unit is called a cartridge for the purpose of this patent application.

The type of filters in the cartridge can be selected to suit the purpose, so for example for filtering dust the filters can be selected which are used in a N95 filter, as known in the art, while for operating safely in an environment with SARS CoV2 the filters as used in filters to comply with standard BSL3 or 4 are selected. One of the filters in such BSL3 or 4 system is an “ultrafilter” like a HEPA or ULPA filter or an electret filter, for removing small sized air born particles which comprise viruses like SARSCoV2. Please note that the average diameter of such virus (about 0.125 micron) is much lower dan the cut off value for a HEPLA filter (about 0.3 micron). Electret filters are known in the art (Lee, 2020; Lin 2017), including their way of manufacture. it is preferred that the virus-retaining filter is combined with one or more coarse filters having a larger pore size, which serve as prefilters. Optionally also a grid can be placed in front of the prefilter located between air supply unit (fan) and the ultrafilter. This helps nucleation and condensation of aerosols, thus increasing their particle size. It is more preferred that the filter cartridge comprises at least 3 filters through which the air must pass: one ultrafilter filter and one coarse filter on each site of the HEPA filter. A coarse filter can for example be a filter having an average pore size of about 0.1-0.4 mm. Preferably the coarse filter is manufactured of a polymer which is polar and can absorb some water in order to help nucleation of condensation of aerosols. The manufacturing process of filter webs is known in the art, and include electrospinning (for example of polyacrylonitrile [PAM] and polyvinylidene [PVDF]) or applying the melt-blowing technique (for polypropylene [PP] or polylactic acid fabrics) (Zhang 2019). It is preferred to use poly-lactate polymers as filter material. Preferably the inlet of the air supply unit (or fan) is equipped with a coarse prefilter as well. The latter can have an average pore size of about 0.6 to 1.0 mm. The filter should create little resistance to air currents which pass the filter. It is placed within, or in front of, the air inlet of the air pump or fan, in order to ensure that dust and larger particles don't enter the pump or fan and cannot block the airflow through the cartridge. The latter prefilter also prevents that people can get hurt by the moving fan, when accidentally approaching it with the fingers.

In one embodiment the filter cartridge is designed to allow cleaning. The cleaning can be done offline, by removing the cartridge and placing it in a second device, or be done “in line”, where the cartridge does not have to be removed. Off line cleaning is for example achieved by taking the cartridge out, connecting it to an air compressor or pump with the outlet to the outlet of the air supply pump, and blowing clean air in reverse direction through it.

In line cleaning can be achieved by applying a suitable construction, as known in the art for reversing flow through a unit which is placed in a line. For example, one could modify tubing construction and place valves before and after the filtering unit. Switching of the valves would reverse the direction of the flow of air through the filter. Due to the weight of motorized valves it is preferred to clean the filter cartridges off line.

A more preferred mode of in line cleaning is done by constructing a cartridge which can be placed in two ways in the housing of the cartridge, one for normal use, and one 180 degrees opposite, which is done for reverse flow and cleaning. By placing a two-way valve in the outlet after the filter, the flow can be directed either in the air guiding system, or to a second conduit during reverse flow/ cleaning. The second conduit guides the air to a place where it can be safely vented, when the protective system is taken off by the wearer.

The air supply system has a motor which is powered by batteries, preferably rechargeable batteries. The batteries are placed close to the motor in or on the second part of the protective device, which allows free movement of the user. Recharging of the batteries can occur by connecting the unit in which these are placed to a recharge unit as known in the art. A suitable adapter can also provide electricity during use, as does light sensitive cells which can be positioned on the second part.

The air supply motor and optionally some valves and LEDs can be regulated by a computerized regulatory unit, which preferably under remote control. So, the filtering unit is characterized by comprising an inlet for air (preferably ambient air), a filter which filters hazardous material from the air, for example viruses or the (larger) particles wherein they are trapped and transported. The second part positions preferably a/ a motorized fan powered by electricity, b/ a power supply unit which are batteries, ¢/ a filtering unit and d/at least a part of an air guiding system. The air guiding system can be separate from the second part, so be attached to it, or form the second part itself by fitting on the head and creating a robust sort of crown to which the other items can be attached. In a more protective embodiment of the invention the second part also comprises a cap which on its own behalf, or in combination with a flexible third part covers the head and hair.

Experiments Analytical method 1: Visualization of particle flows The efficacy and benefits of the different embodiments of the protective system according the invention can be tested by applying methods known in the art for creating volatile droplets in a reproduceable way and blowing these in the direction of a dummy head which is equipped with the protective system. By visualization of the droplets, for example by shining light on the droplets, while the system is placed in a room with a black background, one can observe what happens with these droplets as these approach the dummy head.

The movement and fate of these droplets can also be measured with time by making a film or taking photographs. A high resolution CCD camera, for example one with 2048x2048 pixels, is well suited for making such images. These can be analyzed by applying computer-aided image analyses; for example by calculating optical density of the images. For the analyses of some events high speed photographing may be needed. These data obtained with these measurements allow quantification of results and by comparison with those with prior art systems one can calculate the gain in protection which is obtained by blowing purified air behind the face mask, by means of the air guiding system according the invention.

In this way also the presence of a protective zone around the head of the user of the protective system can be observed. Analytical method 2: Degree of contamination of the face. The following method allows the presence of contamination of the face after using the protective system in a contaminated environment. Again a dummy head is used, but for safety reasons the test with the contamination is applied with a safe marker compound which is dissolved in the liquid that is vaporized and blown in a standardized way to the dummy head. Such marker compound can for example be a fluorescent compound like fluorescein, which has a low detection limit and is easy to detect. After having used the protective system for a standardized time, for example 4 hours, under predefined conditions, a sample is taken from the surface of the face of the dummy head, for example by swapping it with a standard tissue as known in the art. The residue on the swap is analyzed for the presence of the marker compound. This analyses is done by bringing the swab in an Erlenmeyer beaker which contains a suitable solvent which extracts the marker compound from the swab tissue into the solvent. The solvent can be analyzed by for example chromatographic methods, as known in the art. When the marker substance is an inactivated virus, a similar method can be applied, though the presence of the virus in the swab can be identified by PCR.

Analytical method 3: determination of the detection of a marker compound in the lungs.

The following test method can be used to detect and measure the risk for transfer of hazardous substances from the direct environment of the wearer of the protective system into the lungs.

1- Use a hollow real size anatomically correct human dummy head, with an opening at the place of the oral cavity, and connect a hose to the inside of the oral cavity in an air tight manner. The other side of the hose is connected to a powered air pump which is capable of rhythmic pumping and sucking of purified air through this hose at a volume, speed and rhythm, which mimics normal breathing of healthy people. The hose can be equipped with a fresh suitable filter for every for every test, that traps hazardous substances in the lining. For the testing of viruses a sterile filter can be used of fabric or textile.

2- The dummy head is placed in a test setting in front of a source of volatile hazardous substances, either toxic gasses, or droplets of desired size with hazardous substances dissolved or suspended in it. These volatile droplets or gases are in a standardized way generated and blown in the direction of the dummy head, when the test is started. Suitable nozzles for generation of vapors or volatile droplets have been disclosed in the art, as are fans that can propel a defined volume of air in the direction of the dummy head. A suitable distance between dummy head and nozzle is 40 cm to 200 cm, dependent on the question that needs to be answered.

3- The dummy head is equipped with the protective system that will be tested for performance according a provided protocol which ensures adequate fitting the second part around the head, which makes that the first part (or face shield) is in front of the face, the air supply system is fixed on the head, and the air guiding system is positioned to conduit the purified air from the air supply system to the breathing zone. Make sure that the filter system is in place, thus guaranteeing that pure air enters the hose.

4- When a fresh filter is placed in the hose, the pump of the protective system can be activated, which starts the blowing of purified air behind the first part/ face shield

5- Initiate the action of the second pump, thus starting a breathing-like flow of air through the opening in the oral cavity and through the hose with the fresh filter in it. 6- The next step is to activate the fan which blows ambient air in the direction of the dummy head. 7- Then the generation of volatile hazardous substances is started 8- After letting the system operational for a standardized time, for example between one to eight hours, the pump of the protective system, vaporizer, and blower are stopped and the filter in the hose is removed and analyzed for contamination with a hazardous substance.

Analytical method 4: determination of disadvantages of the protective system during routine use A group of volunteers that are representative to a specific group of users is recruited to participate in a phase 2 study. The study serves the purpose to investigate the suitability of using the protective system according the invention in the daily practice of a specific user group, like a health care professional, and compare the experiences with those obtained when using under the same circumstances a second (prior art) system.

The volunteers receive complete instructions how to use the protective system and given ample opportunity to practice putting it on and off and activate the air supply system and replace the filter cartridge and recharge the batteries (or replace the batteries with new charged ones. The volunteers are accurately and complete informed about the investigation protocol, before being asked to give their consent about the study.

The study involves using the protective device during routine daily activities of a specific group of users, such as a nurse, a medical doctor or a care giver, and periodic recording of experiences at predetermined intervals using a standard list of questions. The answers are recorded as a score in the range 1 to 10 (ranking the experience as being absent or being very strong. The results are evaluated by an data analyst that is unaware of what protective system has been used for obtaining the scoring data of the volunteer.

The group of volunteers is randomly split into two groups A and B. The first group A starts with using system | and group B with system Il. One week after the test day with the first system has ended, the group is asked to change the protective system they use and the test day is repeated with the second system. Questions include the experiencing of disadvantages or benefits specific to the systems that are compared and offer a similar degree of protection. For example, the protective system according the invention should be compared with the combination of a mouth mask, eye glasses and a hair net. It can also be compared with a closed helmet with air supply. Alternatively it can be compared with an open helmet with strong air flows. The parameters to measure have been summarized in Table 2. Methods to evaluate cleaning of the system or replacement of the filter cartridge or recharge of batteries are included. Ease of taking the protective system off and storing the system during a pause should be evaluated when the volunteer has used the predefined protocol, which defines all actions to take to do it properly. For example, the ease of intermediate storage during a pause is evaluated when the hook on the protective system for hanging it on a tripod is used. Applying the above-mentioned analytical methods 1, 2, 3 and 4 allows anyone to confirm that the protective system according the invention gives a better performance on at least one of the above-mentioned parameters, (safety, convenience) compared to the protective systems according the prior art.

Figures Preferred embodiments of the invention are depicted in the appended figures 1-5. Fig. 1 shows in perspective a user’s head 3, onto which a protective device 1 according to the invention is positioned in a fixed position, by virtue of a a head- fitting piece 5 which consists of a combination of straps 5 that can be tightened around the head in a common fashion, for instance by using straps 5 of elastic material. Onto one of the straps 5, a filter unit 7 is fixedly attached. Furthermore, a facial cover 9 is fixedly attached to another part of the head-fitting piece 5. The facial cover 9 is dimensioned to cover the entire face of the user's head 3, which facial cover 9 is impermeable to air and in particular to air-borne pathogens and is entirely made from a sheet of transparent material such as polycarbonate. A main duct 25 is provided which is part of a duct system for leading purified air from the filter unit 7 towards the user in order to be inhaled.

Fig. 2 shows a cross-sectional detail of the protective device 1 shown in fig. 1. The filter unit 7 is fixedly attached to the strap 5, and contains a filter inlet 21 for ambient air, a filter 20, and a filter outlet 22 for purified air which is ambient air that has passed through the filter 20. A propeller 23 is provided for propelling purified air from the filter outlet 22 into the main duct 25 of the duct system, and for drawing in ambient air at the filter inlet 21 into the filter unit 7. The main duct 25 is fixedly attached onto the strap 5. Fig. 3 shows in perspective further details of the protective device 1 shown in fig. 1, wherein corresponding elements are indicated by the same reference numbers. The main duct 25 bifurcates into two legs 30 which extend along lateral sides of the face of the user. The whole of the main duct 25 and fluidly connected legs 30, forms the duct system of the protective device. In each leg 30, two exit openings 35 are provided at a vertical location that corresponds to the vertical location of the nose and the mouth of the user. Furthermore, a central exit opening 35 is provided in the duct system at a vertical location corresponding to the forehead of the user.

The facial cover 9 is connected to the straps 5 of the head-fitting piece by a hinge mechanism 33, such that the orientation of the facial cover 9 can be tilted by the user between a covering orientation wherein an air pocket 40 is created as shown in fig. 3, and a non-covering orientation (not indicated, see fig. 4/5), while the head-fitting piece 5 is kept in a fixed position onto the head of the user.

The facial cover 9, has a circumference that is divided in serval peripheral sections 57, 59, 61. At two lateral peripheral sections 59, and one bottom peripheral section 57 the air pocket 40 is in fluid communication with the ambient air surrounding the user's head 3. During use of the device, the air that is present in the air pocket and which contains purified air and air exhaled by the user, is allowed to flow from the air pocket 40 freely at the peripheral sections 57,59 towards the ambient air. The top peripheral section 61 is abutting the forehead of the user, such that at the section 61, the air pocket 40 is not in fluid communication with ambient air, so that air in the air pocket 40 cannot flow freely at the section 61.

The design of the peripheral sections 57,59,61 can be chosen such that an appropriate pressure balance in the air pocket is reached wherein the user can breathe relatively unhindered, while the required inflow of purified air from the duct system is of a practically acceptable value for its purpose. The inflow of purified air should be such that no or only a very limited amount of ambient air can enter the air pocket 40 when the system is used, in other words a slight overpressure is kept in the air pocket during use of the device.

Fig. 4 shows a lateral view of the of the protective device 1 shown in fig. 1, wherein corresponding elements are indicated by the same reference numbers. Fig. 4 shows how the facial cover 9 creates an air pocket 40 which is present between the face of the user and the facial cover 9, so that the user inhales air from the air pocket, and likewise exhales into the air pocket. The user is protected from inhaling ambient air as long as a continuous outflow of purified air is led into the air pocket 40 from the exit openings 35. When the protective device is in use, the duct system achieves that purified air from the filter outlet 22 is led towards all exit openings 35 of the duct system which exit openings are in direct, fluid communication with the air pocket, so that purified air is introduced in the air pocket in a homogeneous manner.

In fig. 4, the facial cover 9 is shown in a covering orientation wherein the air pocket 40 is created. The facial cover 9 that is indicated by a dotted line, shows its non-covering orientation when it is tilted over the hinge mechanism 33.

Fig. 5 shows an alternative embodiment of the protective device 1 shown in fig. 1 and fig. 4, wherein the head-fitting piece 55 comprises a helmet 55, in which the filter unit 7 and the main duct 25 are integrated. The helmet 55 may be part of a protective hood which encloses the head and neck of a user.

Table 1: potential use groups of different embodiments of the protective system Basic Being/ walking in the public domain where a low risk for contamination with an infective pathogenic virus exist and at present primitive mouth masks or face shields are carried Health care professionals which investigate like non- infected people having no disease symptoms Medium Health care professionals, handling potentially infected people with advised distance according a protocol, which at present carry mouth/nose mask, eyeglasses and hair net Maximal protection | Health care professionals , handling infected people with risky operations, and that carry a sort of moon suits, covering the whole body with a closed helmet, and sheets over shoulders and neck Industrial- and military use in hazardous environments

Table 2: Advantages of the protective system according the invention compared to different embodiments of the prior art - Safer than devices without air currents - Allows all operational functions by providing a clear view on the environment and creates less physical constraints than systems having an air supply system on the back with the hoses to provide the helmet with air - Allows face to face communication (compared to masks and moon-suit like helmets - Sounds pass the openings between system and body, allowing speaking and hearing - Easy to put on and off. Positioning is not as critical. Convenient during a pause in the work. Allows scratching when it itches by lifting the shield up and sneezing creates less trouble than conventional face shields or masks.

- Comfortable to wear and use. The helmet is even cooled somewhat. - Less need to wear additional protective devices, like protective eyeglasses or a hairnet; however they can be carried when desired - Provides fresh air instead of air that is mixed with exhaled air like in a mouth mask - Low risk to contaminate others - Does not frighten patients as much - Cheap on the longer term compared to single use devices. The filter cartridge can be regenerated or cleaned. - Much less waste, while it combines the use of hairnet, mouth/nose mask and eye glasses.

Claims (13)

Conclusions A protective device (1) suitable for protecting a user of the device against inhalation of airborne pathogens from the ambient air, the protective device comprising: - a head-fitting part (5) adapted to fit in a fixed position on the head (3) of the user to be placed when the protection device (1) is in use, said head-fitting part being provided with a ventilation system (7, 25) and a face cover (9); - the ventilation system (7, 25) consisting of an air filter unit (7) having an ambient air filter inlet (21), a filter (20), and a purified air filter outlet (22) which is ambient air which has passed through the filter, wherein the ventilation system is arranged to direct the purified air from the exhaust filter (22) to the user to be inhaled; - the face cover (9) adapted to cover at least the mouth and nose of the user when the head-fitting part (5) is placed in a fixed position on the head (3) of the user, which face cover is impermeable to air and especially for airborne pathogens, and the face cover has transparent properties at least in an area of the face cover covering the eyes of the user; wherein, when the protective device is in use, the face cover (9) creates an air space (40) between the user's face and the face cover, the user inhales air from the air space and the user exhales air into the air space; the air space being in fluid communication with the ambient air at one or more peripheral sections (57, 59) of the face cover; the ventilation system including a duct system (25, 30) connected to the filter outlet and through which, when the protective device is in use, purified air is directed from the filter outlet to at least two outlet openings (35) of the duct system which are in direct, fluid communication with the air space (40), so that purified air is introduced into the air space. A protective device according to claim 1, wherein the face cover (9) is sized to cover the entire face of the user when the head fitting is placed in a fixed position on the user's head (3), and preferably wherein the face cover transparent features in an area of the face cover that covers the mouth of the user. A protective device according to claim 1, wherein the face cover (9) is designed as a mouth cap covering the mouth and nose of the user, and does not cover the entire face of the user, especially not the eyes of the user's face, and preferably wherein the face cover has transparent properties in an area of the face cover covering the mouth of the user. The protective device of claim 3, wherein the mouth cap has peripheral sections of which 15% to 30% are peripheral sections where the air bag is in fluid communication with the ambient air. A protective device according to any one of the preceding claims, wherein the head-fitting part (5) consists of a helmet (55) and/or a strap (5), adapted to be fixed on the head of the user. A protective device according to any one of the preceding claims, wherein the channel system (25, 30) forms an integral part of the head fitting (5) and/or the face cover (9). A protection device according to any one of the preceding claims, wherein the ventilation unit (7, 25) includes a propeller (23) for propelling purified air from the filter outlet to the exit openings (35) of the duct system (25, 30), and for drawing in ambient air at the filter inlet (21) in the filter unit, the propeller (23) preferably being electrically driven. Protection device according to one of the preceding claims, wherein the channel system (25, 30) comprises at least one exit opening (35), preferably at least two exit openings (35), which are located at a vertical position corresponding to the vertical position from the nose or mouth of the user, or with a vertical position between the nose and mouth of the user, when the protective device (1) is in use. A protection device according to any one of the preceding claims, wherein the duct system (25, 30) comprises at least two exit openings (35) which are vertically spaced from each other when the protection device is in use, so that purified air is introduced at two vertically different positions in the air space (40), e.g. at a vertical position corresponding to the user's nose and a vertical position corresponding to the user's mouth. A protection device according to any one of the preceding claims, wherein the duct system (25, 30) comprises at least two exit openings (35) spaced horizontally from each other when the protection device is in use, so that purified air is introduced at two horizontally! different positions in the airspace (40), e.g. at sides of the user's face. A protection device according to any one of the preceding claims, wherein the face cover (9) comprises one or more peripheral parts (61) at which the air space is not in fluid communication with the ambient air when the protection device is in use. A protective device according to any preceding claim, wherein the face cover (9) is connected to the head fitting by a hinge mechanism (33) so that the position of the face cover can be tilted by the user between a cover position in which the air pocket is created , and a non-covering position while the head-fitting portion is held in a fixed position on the user's head. A protective hood enclosing the head and neck of a user, which hood comprises a protective device (1) according to any one of the preceding claims.