WO2020101565A1

WO2020101565A1 - Breath analyzing system suitable for helmets

Info

Publication number: WO2020101565A1
Application number: PCT/SE2019/051159
Authority: WO
Inventors: Jonas LJUNGBLAD; Bertil Hök
Original assignee: Senseair Ab
Priority date: 2018-11-14
Filing date: 2019-11-14
Publication date: 2020-05-22
Also published as: SE2150754A1; SE546308C2

Abstract

The present invention relates to a personal protection device, for example a helmet, comprising a breath analyzing system suitable to be provided in a helmet. The breath analyzing system comprises a breath analyzer, a proximity sensor, a communication unit and a flow control assembly arranged to alarm if the breath concentration of a selected intoxicating substance exceeds a predetermined value. The breath analyzing system has a low power inactive mode and an active mode and the proximity sensor is arranged to detect if the personal protection device is worn, and if so, the system changes to an active mode the breath analysis is initiated. The active mode includes initiating an active element of the flow control assembly.

Description

BREATH ANALYZING SYSTEM SUITABLE FOR HELMETS

Field of the invention

The present invention relates to a breath analyzing system suitable to be provided in a helmet. The breath analyzing system comprises a breath analyzer, a proximity sensor, a flow control assembly, and a communication unit arranged to alarm if the breath concentration of a selected intoxicating substance exceeds a predetermined value. In particular, the invention relates to a helmet in which the breath analyzer is activated only if the proximity sensor detects that the helmet is worn properly.

Background of the invention

Vehicles equipped with breath analyzing equipment to detect air-borne intoxicating substances, in particular alcohol, are becoming increasingly common. The breath analyzing equipment may be a stand-alone unit that gives a measured value of the content of an intoxicating substance or substances in the driver’s breath, it may also be part of a system wherein also equipment for identifying the driver and/or immobilizer equipment. To provide a breath analyzer that has an appropriate sensitivity, is reliable and provides a reasonable fast analysis is far from trivial. This is especially true if the breath analyzing equipment should be able to detect a plurality of substances and not being disturbed by variation in moisture, CO2 content etc. Breath analyzing equipment that fulfills these requirements are described in for example US7919754B2 and US9746454B2, hereby incorporated by reference.

So far breath analyzers and system incorporating breath analyzers have been installed mainly in vehicles such as cars and trucks and to a relatively large extent, commercial vehicles. For a number of reasons breath analyzers have been discussed much less in association with open vehicles such as motorcycles and scooters. Given the high number of serious accidents wherein motorcycles and scooters are involved, not at last in regions wherein open vehicles are common for both transportation and commercial use, for example deliveries, a number of initiatives has been taken to improve the security. These initiatives have so far been concentrated on forcing the driver to wear a helmet by making it impossible to ignite the vehicle without wearing a helmet. However, recently more functionality has been

incorporated into helmets that are commonly referred to as“smart helmets” or“intelligent helmets”. A“smart helmet” that incorporate an alcohol detection device is discussed in “Intelligent Helmet”, Jennifer William et al.; International Journal of Scientific & Engineering Research, Volume 7, Issue 3, March-2016, ISSN 2229-5518. To incorporate a reliable and accurate alcohol detection function in a helmet imposes very different demands compared to providing the function in a closed car compartment. Areas of major concerns are for example, but not limited to:

-The size and weight of the equipment added to the helmet. The comfort, and even more importantly, the protective capacity of the helmet should not be jeopardized, which for example adding substantial weight to the helmet would do. Also the appearance is of importance in getting the helmet accepted by a large majority of drivers - the smart helmet should preferably have the same sleek appearance as a regular helmet.

-Power consumption. A smart helmet should preferably be wireless during use. Given the size and weight constrains discussed above, this limits the amount of batteries, and hence power, that can be provided in the helmet. Reliable breath analyzing equipment, exemplified by US7919754B2 and US9746454B2, are typically high power consuming as they are based on Infrared (IR) Spectroscopy for the analysis. There is to date no low power alternative that offers the same sensitivity and ability to detect a range of substances. CN107348596 discloses a helmet that power up an integrated breath analyzing system if a detector or switch indicate that a person is wearing the helmet.

-It is preferred to provide implementations not requiring the driver blowing into a mouthpiece, something that is offered by some car mounted systems and referred to as passive systems. In a helmet a very complex airstream/pressure situation has to be handled if a passive system is to be implemented.

Summary of the invention

The object of the invention is to provide a personal protection device, for example a helmet or a wearable device, comprising a breath analyzing system suitable for being provided in a helmet. Being mounted in a such personal protection device gives constrains to the system with regards to being compact and power efficiency.

This is achieved by the personal protection device as defined in claim 1, the helmet as defined in claim 15, the helmet attachment as defined in claim 15 and the method as defined in claim 18

The personal protection device according to the invention comprises a breath analyzer, a proximity sensor, a control and computational unit and a communication unit. The breath analyzer, the proximity sensor and the communication unit are arranged to be in

communicative connection with the control and computational unit. The breath analyzing system has a low power inactive mode and an active mode. The proximity sensor is arranged to detect the presence of a human skull in the helmet, said detection operable at least during the inactive mode of the breath analyzing system. The control and computational unit is operable in a low power stand-by mode monitoring an input from the proximity sensor at least during the inactive mode, and upon input from the proximity sensor it initiates a change to active mode of the breath analyzing system and activates the breath analyzer. The breath analyzer is arranged to on receiving an activation from the control and computational unit, perform a breath analysis and transmit a representation of the breath analysis to the control and computational unit. The breath analyzing system further comprises a flow control assembly comprising at least one active element and one passive element, providing a gas communication channel from the mouth and/or nose of a user wearing the helmet to an inlet of the breath analyzer and through the breath analyzer. The active element of the flow control assembly is arranged to provide a continuous transport of air to the inlet and through the breath analyzer during the active mode of the breath analysis system.

The personal protection device according to the invention has the advantage of providing an energy efficient system only activating major energy consuming parts as the breath analyzer and the active element than required for performing the breath analysis. The flow control assembly with a combination of passive and active elements ensure that respiratory air is diluted as little as possible and that the time delay is short, both prerequisites for passive detection of for example alcohol.

According to one aspect of the invention at least one passive element of the flow control assembly is formed as an integrated part of the protective structure of the helmet. A passive element may be in the form of an air channel for expiratory air formed in the protective structure of the personal protection device. The channel may be open on the side configured to face the user so that during use that side of the channel is formed by the head of the user.

According to one aspect of the invention the flow control assembly comprises at least one flow guiding structure positioned so that it will be close to the mouth of a user wearing the personal protection device and having a ridge facing the mouth to form a bifurcation of the airflow into the mouth/nose and the airflow out of the mouth/nose of the user.

One advantage of the passive elements is that the control of the transportation of respiratory air is increased. By integrating with the protective structure of for example a helmet an efficient implementation of the breath analyzing system is achieved and comfort and protection is not jeopardized.

According to one aspect of the invention the control and computational unit is arranged to analyze the representation of the breath analysis and compare with at least one predetermined value of an intoxicating substance, and if the predetermined value is exceeded activate the communication unit to issue an alarm. The breath analysis may include the computation of the difference between maximal and minimal readings during a breath cycle of a substance and a tracer signal, said tracer signal representing the concentration of carbon dioxide.

According to one aspect of the invention the flow control assembly includes flow impedances which are either resistive or capacitive and wherein the resistance is dominated by the air flow through a preheater provided in the flow control assembly, the preheater resistance R_h, and the capacitance by the breath analyzer cavity capacitance C _, and the response time xo is given by the relation, xo = R_hC_c, and wherein the response time, xo_, is less than one second, and preferably less than 0.5 second. Sufficiently short response time is a prerequisite in providing an effective and reliable passive breath analyzing system. According to one aspect of the invention the proximity sensor is an ultra-low power proximity sensor, for example a capacitive or an inductive proximity sensor. Alternatively, the ultra-low power proximity sensor is a mechanical switch.

The proximity sensor will be“on” also in the inactive mode of the breath analysis system. By introducing an ultra-low power proximity sensor the power consumption in the inactive mode will be minimized which in turn increases the battery life. Decent battery life could be a key factor for public acceptance of the system.

According to aspects of the invention the breath analyzing system may comprise one or more sensor arranged to detect a condition associated to the usage of the personal protection device, and the control and computational unit being operable in a low power stand-by mode monitoring an input from the proximity sensor and the at least one second sensor; and upon input from the proximity sensor proximity sensor and the second sensor activate the breath analyzer. Second sensor include, but are not limited to, a switch detecting the position of a visor of the helmet, a switch detecting that a mechanical locking mechanism of a strap holding the personal protection device in place is correctly engaged, and indicator of positions of vents on a helmet.

According to one aspect of the invention the personal protection device is a helmet.

According to one aspect of the invention the personal protection device is an attachment configured to be attached to a helmet, for example a collar.

The method according to the invention of performing breath analysis suitable for drivers of open vehicles by the use of a helmet comprising a breath analyzing system comprising a breath analyzer, an proximity sensor, a flow control assembly, a control and computational unit and a communication module, the method comprises the steps of:

-keeping the breath analyzing system in an inactive mode wherein only the proximity sensor is actively in a detecting mode;

- the control and computational unit (12) in the active mode, activating the breath analyzer and the active element of the flow control assembly, the breath analyzer which in response outputs a representation of measured data to the control and computational unit;

-in the active mode the control and computational unit activates the breath analyzer, which in response outputs a representation of measured data to the control and computational unit;

- the representation of measured data is analyzed by the control and computational unit

- the control and computational unit issuing an alarm if the estimated breath concentration of a selected intoxicating substance exceeds a predetermined value;

- if the estimated breath concentration of a selected intoxicating substance exceeds a predetermined value, at least an alarm is activated and if the estimated breath concentration of the intoxicating substance is lower than the predetermined value, the system returns to an inactive mode. In combination with the alarm the open vehicle may be immobilized. The process of checking analyzing the breath may be repeated during the uses of the vehicle, for example at predetermined time intervals.

According to one aspect of the method of the invention the step of turning the breath analyzing system from an inactive mode to an active mode further comprises receiving and analyzing the input from a plurality of sensors or indicators and only if the input from the plurality of sensors or indicators corresponds to a predetermined scheme turn the breath analyzing system from the inactive mode to the active mode. The predetermined scheme may for example specify that the visor of the helmet should be in a closed position and/or that the strap of the helmet is secured.

According to a further aspect of the method according to the invention the step of activating the breath analyzer comprises a pre-step of activating the active element of flow control assembly to give a stable flow of air, including expiratory air, through the sensor module before the actual measurement is performed.

According to one aspect of the method according to the invention the air transport from a user’s mouth/nose to the breath analyzer is effectuated with a time delay considerably shorter than one second. The breath analysis preferably includes the computation of the difference between maximal and minimal readings during a breath cycle of a substance and a tracer signal, said tracer signal representing the concentration of carbon dioxide.

According to one aspect the method further comprises a step of immobilizing the open vehicle if the estimated breath concentration of a selected intoxicating substance exceeds a predetermined value. Afforded by the present invention is the possibility to use a breath analyzer which is based on the principle of non-dispersive infrared spectroscopy (NDIR) to allow adequate accuracy, specificity and reliability, and confined in a breath analyzer cavity having physical dimensions small enough to be integrated inside a helmet.

One advantage of the present invention is that the function of the helmet with respect to the personal safety of its carrier is not compromised. This is ensured by the system according to the invention being an integral part of the helmet or constituting a separable physical enclosure. From the points of view of testing and quality assurance, the second alternative is particularly attractive. One advantage is that the breath analyzing system may be adapted to various kinds of helmets, such as open helmet and full-face helmets.

Low power consumption and attractive features increases the likelihood of the equipment being used. Low power consumption of the breath analyzing system is a requirement on its own, but an additional effect is that power can be saved to other systems that might attract a driver more than a breath analyzing system, for example a GPS navigator with on-visor display.

In the following, the invention will be described in more detail, by way of example only, with regard to non-limiting embodiments thereof, reference being made to the accompanying drawings.

Brief description of the drawings

Fig. la-b are schematic illustrations of the helmet according to the present invention in (a) a semi cross-section view and (b) in a view from below; Fig. 2 is a schematic illustration of the functional units of the present invention;

Fig. 3 is a schematic illustration of one embodiment of the helmet according to the present invention;

Fig. 4 is a schematic illustration of the ultra-low power proximity sensor according to the present invention; Fig. 5 is a schematic illustration of the functional units of the helmet node and the open vehicle node according to one embodiment of the present invention;

Fig. 6 is a logical circuit of the switching functionality according to one embodiment of the invention;

Fig. 7 a-b are graphs illustrating the analyzed CO2 content and detected substance at different time as detected by the breath analyzer of the present invention;

Fig. 8 is a schematic representation of the function of the flow control assembly including its basic constituents provided in the helmet according to the present invention;

Fig. 9 is a flowchart of the method according to the present invention;

Fig. 10 illustrates one embodiment of an additional helmet module according to the invention.

Detailed description

Terms such as’’top”,“bottom”, upper”, lower”,“below”,“above” etc are used merely with reference to the geometry of the embodiment of the invention shown in the drawings and/or during normal operation of the helmet and are not intended to limit the invention in any manner.

The term“open vehicle” is herein used to encompass all vehicles for which a helmet is commonly recommended for the driver and passengers. Open vehicle includes, but is not limited to, motorcycles, scooters, tricycles, quads/ AT Vs, snowmobiles and speedboats.

The present invention relates to a personal protection device provided with a breath analyzing system. The personal protection device could be a helmet or an attachment to a helmet, for example a collar to be worn together with a helmet. The personal protection item is primarily described as a helmet for the ease of description only and all features and variants are relevant for all personal protection items, if not otherwise stated.

A helmet according to the present invention comprising a breath analyzing system 3 is schematically illustrated in Figures la-b, wherein a) is a partly cross-sectional sideview of the helmet and b) is a view of the helmet from below. Figure 2 is a schematic illustration of the functional units of a breath analyzing system according to the invention. The helmet 1 comprises a visor 2, which may be movable and is depicted in a downward position. The breath analyzing system 3 of the helmet 1 comprises a breath analyzer 6 with an analyzing chamber 6b forming a cavity in which a breath sample is analyzed, a proximity sensor 7, a controller and computational unit 12, a communication unit 13 and a power supply 15. The breath analyzer 3, the proximity sensor 7 and the communication unit 13 are arranged to be in communicative connection with the controller and computational unit 12. The breath analyzer 6 is provided with an inlet 16 and an outlet 17. A flow control assembly 11 is provided in fluid communication with the inlet 16, or the outlet 17, or both the inlet 16 and the outlet 17. The inlet 16 may include a heater element, e g a serpentine conducting foil or metallic wire grid, to prevent condensation of water droplets within the breath analyzer cavity 6. The heater constitutes the dominant air flow resistance of the flow control assembly 11, the functional significance of which will be further described in relation to Figure 8. The flow control assembly 11 comprises passive elements and at least one active element 1 la to control the air flow within the helmet 1. The passive elements are operative to provide selected air passages to the respiratory air flow and the active element 1 la to actively transport at least a portion of the respiratory air flow. The active element 1 la of the flow control assembly 11 is in communicative connection with and is controlled by the controller and computational unit 12.

According to one embodiment the active element 1 la of the flow control assembly 11 is a flow generating device 11a provided in connection to the analyzing chamber 6b. Preferably, the flow generating device 11a comprises a miniature fan, and also a flow measurement device with a tachometer control function. The flow generating device 11a can be controlled by the controller and computational unit 12. According to one embodiment the flow generating device 1 la is provided after the analyzing chamber 6b in the direction of the airflow, as this generally is a preferred way to ensure a steady and predictable air flow through the analyzing chamber 6b. Alternatively, the flow generating device 11a may be positioned elsewhere in the flow control assembly 11, which could be a design choice considering other design parameters of the helmet, such as safety, comfort and weight distribution.

The proximity sensor 7 is according to one embodiment an ultra-low power proximity sensor designed and arranged to detect the presence of a human skull in the helmet. Preferably the ultra-low power proximity sensor 7 requires a minimum of power during a non-detecting state and also only a small amount of power for the actual detection of a skull and for

communication with the control and computational unit 12. The ultra-low power proximity sensor 7 may be a capacitive or inductive proximity sensor. Such ultra-low power proximity sensors are known in the art and will be further discussed below. The proximity sensor 7 may also comprise a plurality of sensors and/or switches arrange to, in combination, detect the presence of a skull in the helmet 1 and also other conditions associated to the driver being driving or about to start driving. Such additional sensors/switches include, but is not limited to sensors indicating the position of a visor of the helmet, the driver having mounted the vehicle etc.

Suitable breath analyzers are known and commercially available from for example Senseair AB. As discussed in the background breath analyzers with required physical size and weight for helmet integration, sensitivity, reliability and speed of detection typically relies on IR- spectroscopy, which make them consume considerably amounts of energy during operation. The breath analyzer 6 is arranged to respond to the intoxicating substance, and to a respiratory tracer gas generally occurring in expiratory air, e g CO2 or H2O. Preferably the breath analyzer is based on infrared spectroscopy, including an infrared source, a detector, and optical filters with passband adapted to absorption bands of the substances to be analyzed. In the case of ethyl alcohol as the intoxicating substance, an absorption band at 9.5 pm is used. Corresponding absorption band for CO2 is 4.3 pm. These design principles are enabling high sensitivity and specificity to the selected substances. The breath analyzer 6 according to the invention is arranged to have a low power inactive mode, including a completely switch off mode, and an active mode. The breath analyzer 6 is turned on or put in active mode by the control and computational unit 12 and then perform a breath analysis and transmit a representation of the breath analysis to the control and computational unit 12 and after the breath analysis is performed return to the inactive mode or to being turned off.

The control and computational unit 12 is preferably a general-purpose microcontroller operating on digital signals to perform logical and arithmetic operations according to a pre programmed scheme. It may calculate the breath concentration of the intoxicating substance by multiplying the actual measured value by the appropriate dilution factor determined by breath analyzer element responding to the tracer gas. The control and computational unit 12 is being operable in a low power stand-by mode essentially only monitoring an input from the proximity sensor 7. The detection of a signal from the proximity sensor 7 acts as trigger to activate the control and computational unit 12 into an operational mode and in sequence activate the breath analyzer 6 in combination with the active element 1 la of the flow control assembly 11. Also the the communication unit 13 may be activated. Also other conditions may be required for the control and computational unit 12 to activate the breath analyzer 6. From a system level the breath analyzing system 3 may be described as having an inactive mode, which is characterized by a minimum of power consumption, wherein only parts required for a first detection of the helmet being used is active and an active mode wherein breath analysis and communication is performed.

The power control unit 14 is preferably managing proper power supply to all system components. It is preferably driven by a power supply 15, which may be a rechargeable battery, preferably a high capacity battery such as a lithium-ion battery. The power control unit 14 may be connected with power harvesting devices harvesting energy from electromagnetic radiation, sun, motion or other energy sources, which can be used momentarily or to charge the battery.

According to one embodiment at least one passive element of the flow control assembly 11 is formed as an integrated part of the protective structure of the helmet 1 and the flow control assembly 11 is arranged to direct air up around the head and into the breath analyzer. The integrated part may for example be, but not limited to channels transporting air, in particular expiratory air, a flow guiding structures assisting in directing the air or providing separation between airstreams or sealing members. According to one embodiment illustrated in Figures la-b, the flow control assembly comprises the flow generating device 1 la, at least a front air channel 1 lb and at least a rear air channel 1 lc. A modem helmet 1 is typically built up by a hard outer shell lb, an impact absorbent liner lc and a comfort liner Id forming the protective structure. The front air channel 1 lb and the rear air channel 11c may be arranged in either the impact absorbent liner lc or a comfort liner Id or extends over both liners. The front air channel 1 lb and the rear air channel 11c may be realized by a number of channels that are joined to the inlet 16 and the outlet 17, respectively. The front air channel 1 lb and the rear air channel 11c typically have a depth, i.e. their extension in the radial direction, in the order of lcm. The front air channel 1 lb may preferably be shaped as a funnel with a substantially wider opening, in the direction of the helmet’s inner circumference, at the front end, towards the persons face, than at its rear end joining the inlet 16. Preferably the width at the front end of the front air channel 1 lb is in the order of 5 cm or larger. In order to not impair with the impact function or the comfort of the helmet an air channel, for example front air channel 1 lb, may in its wider parts, be divided into a plurality of thinner channels, or having a plurality of impact absorbent protrusions extending in the radial direction. The rear air channel 11c may end as depicted close to the user’s neck. Alternatively the rear air channel 11c ends in one or more vents (not shown) provided in the rear part of the helmet 1. Such vents typically exist on modem helmets in order to provide means for ventilation.

According to one embodiment at least one air channel is an open elongated recession in the protective structure, so that during use the user's head forms one wall of the channel. The comfort liner Id in the helmet is often removable, for cleaning and/or personal adjustment, and may comprises of a plurality of different parts referred to as pads. One alternative is that the front air channel 1 lb and the rear air channel 1 lc are formed as intentional gaps between separate comfort liner pads. The air flow directed by the flow control assembly 11 is indicated with arrows in Figure 1.

Air enters the helmet inlet area 4 and is either mixed with the person’s expiratory air or partly inhaled by the person depending on the actual instant within the person’s respiratory cycle. The air is further drawn upwards inside the closed visor 2 and then passes through the breath analyzer 6 to the helmet flow outlet 5 at the neck of the driver. The airflow is driven and controlled by the flow generating device 1 la to pass through the inlet 16 and outlet 17 of the breath analyzer 6. Preferably, the flow generating device 6b is a miniature fan, including a flow measurement device with a tachometer control function. The inner surface of the visor 2 and other inner surfaces of the helmet 1 preferably includes material which is non-absorbing with respect to the intoxicating substance, e g a fluoropolymer.

According to one embodiment the air is transported driven by the flow generating device 6b and via air one or more channels provided in the protective structure of the helmet 1, for example in channels provided in padding.

The flow control assembly 11 may include one or several flow guiding structures. According to one embodiment flaps l id, 11c preferably made from non-absorbing polymer foam are arranged on and extending from the inner surface of the helmet 1 close to the breath analyzer cavity 6 and forming a flexible, yet tight contact surface towards the person’s skull. The flaps 11c, 1 Id are given a curved surface to allow a smooth and laminar air flow.

According to one embodiment a flow dividing structure 1 le is attached to the inner surface of the visor 2. Preferably, the structure l ie includes an edge, rim or equivalent, guiding airflow to pass on either side of it. By guiding expiratory air in an upward direction while allowing inspired air to pass unhindered towards the mouth or nose of the person, the flow dividing structure l ie defines a flow bifurcation point Q between the part extending upwards, and the part of expired flow moving downwards to the ambient.

Furthermore, the air passages in the flow control assembly 1, for example between the helmet’s inner surface and the person’s skull, or in the front air channel 1 lb and the rear air channel 11c, are carefully dimensioned and designed to control the flow impedances along the flow path. A more detailed description of the air flow dynamics is provided in relation to Figure 8.

The helmet 1 according to the invention preferably includes a mechanism to prevent it from being involuntarily removed from its proper position by translational or rotational movement. By example, a strap band 18 is locked into position across the chin of the person wearing the helmet with a spring latch 19 including a microswitch signaling locking or unlocking position. Alternatively, the visor 2 may in the locked position be covering the chin of the person to prevent removal.

The result of a breath analysis, at least if the result indicates the existence of an intoxicating substance in a concentration surpassing a predetermined value, is presented to the user. This is performed by the control and computational unit 12 engaging the communication unit 13 to communicate the result directly to the driver as an audio-visual warning, for example, or to a receiving unit on the open vehicle, which issue a warning, for example an audio-visual warning to the user. Alternatively, the receiving unit of the open vehicle is in connection to an immobilizer unit that upon the detection of an improper concentration of the intoxicating substance hinder the ignition or turn off the vehicle if it is already running. The latter action needs of course to be done in a manner that does not jeopardize the safety of the driver or others.

According to one embodiment of the invention the communication unit 13 is a wireless communication unit preferably using a standard protocol such as Bluetooth, Zigbee or NFC for the communication with an external unit, for example a receiving unit on the vehicle. The communication unit 13 may be used also for other purposes, it may for example be integrated with a Bluetooth headset for communication with a smartphone or intercom devices.

Alternatively or additionally the communication unit 13 may be provided with

communication means, for example a 4G communication unit, to communicate with telecommunication networks or other wide area networks.

Figure 3 illustrates schematically an alternative embodiment of a helmet 101 according to the invention. The helmet 101, a so called fullface helmet, comprises a transparent part 102 located in front of the eyes of the person carrying the helmet 101. The transparent part 102 may be movable. The helmet 101 comprises a chin bar 120 below the transparent part 102 and partly in front of the mouth of the person.

The breath analyzing system 103 comprises a breath analyzer 106 with an inlet 116 and an outlet 117, corresponding to the breath analyzer 6 of Figures 1 and 2, and is located on the inside of the chin bar 120. When the person emits expired air flow 104 it will directly impinge on the breath analyzer 106, whereas inspired air flow 105 will clean the area from expiratory air.The breath analyzer 106 is similar to the above described embodiments provided with an flow generating device and preferably also a pre-heater.

The air flow conditions are somewhat different in the embodiments of Figures 1 and 3, mainly due to the different positions of the breath analyzer cavities 6b and 106, respectively. When the cavity 106 is positioned right in front of the person’s mouth and nose, the air flow can be concentrated to this region. This difference is, however, quantitative in nature, rather than qualitative. Basically, equivalent elements of the flow control assembly 11/111 need to be present in both cases, including at least one active element, the flow generating device, required to ensure adequate gas exchange through the breath analyzer cavity 106 and causing an exhaust air flow 110 and at least one passive element preferably integrated with the interior of the helmet 101. The dominating flow resistance from the preheater of the inlet of the breath analyzer 106 remains as a common element in both embodiments.

According to one embodiment the passive element of the flow control assembly 111 is a flow guiding structure 111 positioned at the inlet of the breath analyzer 106. It is designed to separate the exhaust air flow 110 from the incoming flow 104. The edge or rim directed towards the person’s mouth of the structure 111 defines a bifurcation point analogous to the flow guiding structure 1 le in Figure 1.

According to one embodiment, the full face helmet 101 is provided with a proximity sensor 107 used for activating the breath analyzer system 103 analogously to the function described in relation to Figures 1 and 2. A further proximity further sensor 107’ or sensors may be provided to indicate the position of the user's head. The embodiment of the helmet in Figure 3 may further include a mechanism to prevent the helmet from being involuntarily removed from its proper position by means of a strap band 108 and a locking mechanism 109.

The breath analyzing system 3 in the embodiments illustrated in Figures 1 and 3 may be provided with a physical casing including protective material, e g polymer foam, to minimize impact damage on the human skull. Alternatively, the breath analyzing system 3 is made as an integral part of the protective padding of the helmet 1.

Figure 10 illustrates an embodiment of the personal protection item according to the invention realized as a U-shaped collar 201 designed to be attached to, or integrated with, the lower circumference of a helmet 200. The collar 201 comprises two legs 201a; 201b provided with through channels 21 la; 21 lb which extends from a chin position 220 to the breath analyzer 206. The through channels 21 lb; 21 lc as well as a flow generated device 2011a provided at the breath analyzer and an outlet channel 21 Id are parts of the flow control assembly. The through channels 21 lb, 21 lc of the collar 201 represents passive elements integrated in the protective structure and the flow generating device 211a represents an active element. During use, the air flow is actively driven from the chin position 202 through channels 210a; 21 la and then passes through a breath analyzer 206 before being emitted to the ambient air through the outlet channel 21 Id. In this embodiment, the breath analyzer 206 comprises all the necessary elements including the breath analyzer with the breath analyzer cavity 203, proximity sensor, control, computational and communication units, and flow generating device 211a, although not all of these elements are explicitly drawn in Figure 10.

The embodiment in Figure 10 differ from to those of Figures 1 and 3 in that the breath analyzing system 3 being physically separable from the helmet. Therefore, the protective properties of the helmet are uncompromised and can be tested independently from the presence or absence of the system according to the invention. Furthermore, the collar-shaped design and position is advantageous from a flow control perspective. One advantage of this embodiment is that the dead space between the person’s mouth and the inlet 16 of the breath analyzer cavity 6 is minimized, which improves the system response time. Furthermore, the positioning of the main system components at the backside of the helmet in Figure 10 is not intrusive to the person carrying the helmet.

Figure 4 illustrates the function principle of one embodiment of the proximity sensor 7, in the form of a ultra-low power proximity sensor. The sensor includes a resonator 45 illustrated as an inductor and capacitor connected in parallel. The resonating frequency is determined by the magnitude of these reactive elements, and also to some degree by the resistive loss always present. The quality factor is determined by the magnitude of this loss in relation to the stored energy in the reactive elements at resonance. Using the piezoelectric effect, electromechanical resonating elements may be combined with electromagnetic elements. More specifically, quartz resonators allow a quality factor of 10⁶ or even higher to be obtained which is preferable, both from the point of view of sensitivity and of power consumption. The resistive loss and the resonance frequency is influenced by the presence of conductive tissue 48, for example a human skull, in the proximity of the resonator. An oscillator circuit 46 is configured to oscillate at the resonance frequency of the resonator, and a trigger circuit 47 is detecting small shifts of the oscillating frequency, and its output signal is used for switching the system from the inactive mode into an active mode of operation as described above and further discussed below with reference to the flowchart of Figure 8. The total power consumption of the ultra-low power proximity sensor according to the invention is less than 10 pW.

Figure 5 shows one embodiment of the breath analyzing system 3 according to the invention adapted to be used to permit a sober person wearing a helmet to drive a motorcycle while preventing an intoxicated person to do the same. The system is adapted to also prevent driving without a helmet. The system includes one helmet node 51 and one motorcycle node 58 (with mutual two-way, wireless data communication.

The helmet node 61 is basically configured in the same way as was previously described in relation to Figure 2. It includes a control and computational unit 52, a data communication unit 53, a power control unit 54, a flow control assembly 55 with at least one active element controllable by the control and computational unit 52, a breath analyzer 56, and a proximity sensor 57. These units correspond to the units 12, 13, 14, 15, 16, 17 in Figure 2.

The open vehicle node 58 includes one data communication unit 51 configured for two-way wireless data communication with the helmet node 51 following Bluetooth, Zigbee, or other standards for short-range wireless data communication. Also included is a control and computational unit 59 comprising a standard microcontroller with internal memory and programming capabilities. The sensor unit 60 may include sensor elements to establish the exact position of the vehicle, its speed and other entities of interest, for example based on the Global Positioning System (GPS). A power control unit 62 is also included. This may control both the open vehicle node 58 and remotely also the helmet node 51 when this is in a ‘sleeping mode’ as described in relation to Figure 2.

The open vehicle node 58 may also include an immobilizer unit 63 which is basically a switch configured to enable or disable driving or the open vehicle by controlling the ignition, the steering or other critical functions of the open vehicle. The immobilizer 63 is controlled by the control and computational unit 59.

The“smart helmet” described with reference to Figure 5 may be extended to include also other sensors and functions. As described, the proximity sensor 57 can be used not only to activate the system, but also to ensure that the driver actually wears the helmet, in that the control and communication unit of either the helmet or the open vehicle is arranged to not activate the immobilizer unit if and only if both the proximity sensor 57 signals that the helmet is worn and that one or more intoxicating substance is below a predetermined value. Further sensors may be utilized. It is for example plausible that, depending on the design of the helmet, the visor 2 or transparent part 102 has to be in a downward position in order to provide for a stable and predictable airflow to the breath analyzer 6, 106. In that case a visor sensor could sense the position of the visor and ensure that the visor is in the correct position for the breath analysis. Alternatively, the information from the visor sensor could be used to influence the flow control assembly 11 to change the settings depending on the indications from the visor sensor. Biometric devices could also be incorporated in the system to ensure the correct identity of the driver. Bluetooth communication offers a way to gain knowledge of the distance between two communicating units, information that could be used to activate the breath analysis procedure only if the driver is actually on, or in close vicinity to, the open vehicle.

Figure 6 describes, by means of example, the logic circuitry controlling the switching of the breath analyzing system 3 to and from active and standby mode, respectively according to one embodiment of the invention. The overruling principle is to establish the occupancy and secured position of the helmet with reasonable certainty. The occupancy should in turn determine if and when the system should be activated. In some applications when carrying a helmet is mandated by law or other means, it is important that the determination of occupancy is reliable. Employing a plurality of independent indicators 81, 82, 83 is an arrangement to achieve this, wherein one indicator 83 corresponds to the above described proximity sensor 7, preferably an ultra-low power proximity sensor.

The circuitry includes a plurality of digital indicators 81, 82, 83 whether or not the helmet is worn in a secure way by a user. The electromechanical switches 81 and 82 will close by contacting or by movement when the helmet is taken on, thereby being switching from Tow’ to‘high’. One of the switches 81, 82 can be activated by the visor (2 in Figure 1), and another switch one could, for example, be activated by a strap to secure fastening of the helmet to the skull. A further alternative is that the helmet may be provided with one or more vents that often can be manually opened or closed in order to regulate the ventilation of the helmet. The switches 81, 82 may be associated with the vents and indicated a position of the vents that is suitable for the breath analysis to be performed, for example and typically the vents being in a closed position. Via the communication unit 13 and the communication unit 13 the driver may be informed to take the necessary actions to get the switches in the required positions for the breath analysis to be performed. The output of the proximity sensor 83 will correspondingly go from’low’ to‘high’ when the presence of a human skull is detected, as previously described in relation to Figures 1-2. A timer circuit 84 is receiving signals from the switches 81, 82 and the proximity sensor 83 and is programmed to provide a‘high’ signal if these signals occur in a correct sequence according to a preprogrammed schedule. In its simplest implementation, this schedule is the order in which the switches 81, 82 and/or the proximity sensor 83 are indicating occupancy. The schedule could alternatively involve other logical functions. The output of the logical‘AND’ gate 85 will go from Tow’ to‘high’ when and only when the signals from the switches 81, 82, the ultralow power proximity sensor 83 and the timer 84 all are‘high’. Then the system according to the invention will turn from standby to active mode. The circuit elements of Figure 6 are preferably comprised of CMOS switches with extremely low power consumption both in their static‘high’ and Tow’ conditions, and when switching between these conditions. The total power consumption of this control circuit will not exceed 1 pW.

Figure 7 shows a simultaneous recording of CO2 concentration (top graph) and the concentration of ethyl alcohol representing an intoxicating substance (bottom graph). Three consecutive high CO2 concentration peaks 71, 72, and 73, occur with a few seconds interval with the concentration returning to a minimum reading 74 in between. The peaks coincide with alcohol concentration peaks 75, 76, 77 compared to the minimum reading 78. The difference between maxima and minima of CO2 readings is used for estimating the dilution of the recorded peak concentrations based on the physiologically defined alveolar CO2 concentration of approximately 4.2 vol%. An estimate of the alveolar intoxicating substance concentration is then calculated from the measured substance peak concentration difference and the dilution.

Response time of the breath analyzing system 3 according to the invention is considerably shorter than one second or the time interval between two breaths. The airflow control facilitated by the breath analyzing system lis such that the time of gas transportation and exchange is considerably shorter than one second or the time interval between two breaths.

One intoxicating substance the breath analyzing system 3 according to the invention could be arranged to detect is ethyl alcohol. Other substances include, but is not limited to opiates, cannabis and various pharmaceutical compounds known to affect the ability to handle a vehicle.

Figure 8 is a circuit model of the air flow control assembly 11 according to the invention. Circuit modelling of this kind is customary to describe the behavior of interconnected passive and active elements in electronics, pneumatics, hydraulics, and acoustics (see e g R. T.

Weidner, R. L. Sells Elementary Classical Physics, Allyn and Bacon, 1965, pp. 753-780, 901- 931). The model in Figure 8 includes the respiratory air flow generated by the person wearing the helmet, and the circuit elements of the flow control assembly 11. The active element G_r is representing the person’s respiratory, bidirectional flow. At rest the flow rate is typically 0.5 liters per breath, both at expiration and inspiration. The duration of one expiration is typically one second. The other active element G_f is the flow generating device driving air through the breath analyzer cavity 6, typically at a constant rate of 0.3 liters per second across a pressure difference of 50 Pa. The volume of the breath analyzer cavity 6, 106 is typically less than 0.02 liters, with physical dimensions 60 x 30 x 10 mm. The transit time of air through the cavity is therefore typically 0.02/0.3 = 0.067 seconds. Flow generating devices of this kind are available from several manufacturers, including SEPA GmbH, Germany, operating in both axial and radial modes, and having dimensions smaller than 45 x 45 x 5 mm. The embodiment shown in Figure 3 will not require as high capacity as that in Figure 1. Therefore, the flow generating device in the Figure 3 embodiment may be smaller.

The two active elements G_rand G_f are interconnected as illustrated by the circuit diagram in Figure 8 by passive flow impedances which are either resistive or capacitive. The magnitude of the resistive elements is proportional to their length and inversely proportional to their cross-section area. The magnitude of capacitive elements is proportional to their volume.

A critical condition of the flow control assembly is to provide adequate coupling between the respiratory generator G_r to the measuring circuit arm defined by the transfer impedances R_ti//C_ti and R //C_t2, the preheater resistance R_h,the breath analyzer cavity C _, and the flow generator G_f. R_h constitutes the dominating resistive element of typically 1.5 * 10⁵ Pa/m³/s. The transfer impedances R_ti//Cu and R //C_t2 are dominated by their reactive constituents Cu_, C_t2 compared to the resistive parts Ru and R_t2. Typically, the total transfer volumes range from 0.05 to 0.2 litres. The smaller number refers to the embodiment in Figure 3, whereas the embodiment in Figure 1 is represented by the larger number. In both cases, the mean transit time is less than one second. The establishment of a well-defined flow bifurcation point Q is critical to provide adequate division of air flow between the measuring arm to the right-hand side of G_r, in Figure 8, compared to the shunting left-hand side. If the shunting impedance R_s//C_s is very small, it will effectively short circuit the measuring arm, and the signal output will be inadequate. The physical implementation of a bifurcation is exemplified by the flow guiding structure l ie shown in Figure 1 and 104 in Figure 3.

The present sensor technology can accept a dilution of 1 : 10 corresponding to 90% shunting of the generated breath flow through R_s//C_s. This condition can be met in the embodiments described in Figures 1 and 3 by inclusion of flow guiding structures for flow path separation, adequate definition of bifurcation points, and using a spacing of 10 mm between the skull and the inner helmet surface. The latter criterion is also based on a further condition that the person’s respiratory gas exchange shall not be hampered by an excessive flow impedance.

The response time xo is determined by the equation xo = R_hC_c = 0.03 seconds according to the numerical data provided above, less than half the transit time. Both numbers are consistent with a required total response time of less than one second.

Figure 9 is a flowchart over the method of performing breath analysis suitable for drivers of open vehicles according to the invention using the sensor system according to the invention. The method comprises the steps of:

805: Inactive mode. The breath analyzing system is in an inactive mode characterized by that only one sensor/indicator or indicator or a limited set of sensors/indicators, referred to as the proximity sensor 7, is actively in a detecting mode

810: Detecting breath analyzing conditions. If the proximity sensor 7 is activated by detecting that the user is using the personal protection device 1, 101, 201 in a correct manner, for example detecting the presence and position of a human skull within the helmet 1 or that collar 201 is correctly positioned around the neck, the system is turned from an inactive mode with very low power consumption into an active mode, step 815. If not, the system remains in inactive mode.

The system going to active mode may require a plurality of actions/events or a combination of such actions/events, which are referred to as triggers:

a) the proximity sensor 7 detects that a person is wearing the personal protection device 1,

101, 201; b) the visor 2 is in a closed position as sensed by a visor indicator 81;

c) the strap of the helmet is closed as sensed by a strap indicator 82;

c) communication units, or other units, indicating that the personal protection device 1, 101, 201 is close to the open vehicle;

d) during operation initiate breath analysis at predetermined time intervals;

e) verifying the identity of the driver, for example using biometric data.

815: Active mode and Initiating respiratory activity. The control and computational unit 12 sets the breath analyzing system to an active mode and activates the breath analyzer 6 and the flow generating device 1 la of the flow control assembly 11. The breath analyzer 6 in response outputs a representation of measured data to the control and computational unit 12.

820: The control and computational unit 12 receives and analyzes the representation of measured data from the breath analyzer 6. Respiratory activity is detected by the tracer gas responding element of the breath analyzer 6 as an expiratory peak of tracer gas, e g CO2, or H2O. The output of the breath analyzer element responding to the intoxicating substance indicates whether intoxicating substance is present in the expiratory airflow from the driver.

825: Substance detection. If the estimated breath concentration of a selected intoxicating substance exceeds a predetermined value, an alarm is activated, step 830. If on the other hand the estimated breath concentration of the intoxicating substance is lower than the

predetermined value, the system returns to an inactive mode, step 835.

830: Alarm. The driver is informed of the result that the estimated breath concentration of a selected intoxicating substance exceeds the predetermined value, for example by an audio visual signal. The signal may be issued by the communication unit 13 of the helmet 1, or alternatively the communication unit 13 communicates with a receiving unit of the open vehicle, which issues the alarm.

831 : Prohibit driving: In an optional step or as alternative to, or in combination to the alarm of step 830, an immobilizer unit of the open vehicle is activated via the communication unit 13 and a receiving unit of the open vehicle.

835: return to inactive mode. The breath analyzing system is turned into the inactive mode. The method may also comprise the steps of: 840: Time limit. If repeated breath tests are utilized, the procedure is repeated after a predetermined period of time, during the waiting time the system remains in the inactive mode, step 810.

As realized by the skilled person, certain steps in the method can be performed in various units. For example, the computation of the measured result may be performed by a computational unit on the open vehicle instead of being performed in a computational unit of the helmet. In that case all“raw data” is transferred to the open vehicle unit.

The step of turning to active mode and initiating respiratory activity, step 815, may include a pre-step of activating the active element of the flow control assembly 11 to give a stable flow of air, including expiratory air, through the sensor module.

Upon detection of a selected intoxicating substance exceeding a predetermined value a second breath analysis may be initiated before issuing the alarm in order to minimize the risk for the result being a faulty measurement. As a complement to having a predetermined value that is not allowed to surpass, a range below that predetermined value could result in a milder form of alarm, for example if linked to a immobilizer, the immobilizer is not activated but the driver is informed about the existence of the intoxicating substance. A concentration of an intoxicating substance in a range below the predetermined value could also trigger a more frequent repetition of the breath analysis.

The embodiments described above are to be understood as illustrative examples of the system and method of the present invention. It will be understood that those skilled in the art that various modifications, combinations and changes may be made to the embodiments. In particular, different part solutions in the different embodiments can be combined in other configurations, where technically possible.

Claims

1. A personal protection device (1, 101, 201) comprising a breath analyzing system (3) comprising a breath analyzer (6, 106, 206), a proximity sensor (7, 107), a control and computational unit (12) and a communication unit (13) , the breath analyzer (6, 106, 206), the proximity sensor and the communication unit (13) arranged to be in communicative connection with the control and computational unit (12)

characterized in that

-the breath analyzing system (3) comprises a flow control assembly (11) comprising at least one active element (11a, 211a) and one passive element, providing a gas communication channel from the mouth and/or nose of a user wearing the helmet (1, 101) to an inlet (16) of the breath analyzer (6, 106, 206) and through the breath analyzer (6, 106, 206);

-the breath analyzing system (3) having a low power inactive mode and an active mode;

-the proximity sensor (7, 107) is arranged to detect the presence of a human skull in the helmet (1), the proximity sensor (7, 107) operable during the inactive mode of the breath analyzing system (3);

-the control and computational unit (12) adapted to react on an input from the proximity sensor (7, 107) and initiate a change to active mode of the breath analyzing system (3) and activate the breath analyzer (6, 106, 206) and the active element (11a, 21 la) of the flow control assembly (11);

-the breath analyzer (6, 106, 206) arranged to, on receiving an activation from the control and computational unit (12), perform a breath analysis and transmit a representation of the breath analysis to the control and computational unit (12);

2. -the active element (11a, 211a) of the flow control assembly (11) arranged to provide a continuous transport of air from the user wearing the helmet to an inlet 16 of the breath analyzer (6, 106, 206) at least during the breath analysis.

3. The personal protection device (1, 101, 201) according to claim 1, wherein at least one passive element of the flow control assembly (11) is formed as an integrated part of the protective structure of the personal protection device (1, 101, 201).

4. The personal protection device (1, 101, 201) according to claim 2, wherein the flow control assembly (11) comprises at least one channel (1 lb, 11c, 211b, 221c) for expiratory air formed in the protective structure of the personal protection device (1, 101, 201), wherein the channel is open on the side configured to face the user so that during use that side of the channel is formed by the head of the user .

5. The personal protection device (1, 101, 201) according to any of claims 2 to 3,

wherein flow control assembly (11) comprises at least one flow guiding structure (l id, 111) positioned so that it will be close to the mouth of a user wearing the personal protection device (1, 101, 201) and having a ridge facing the mouth to form a bifurcation of the airflow into the mouth/nose and the airflow out of the mouth/nose.

6. The personal protection device (1, 101, 201) according to any of the preceding claims, wherein the control and computational unit (12) is arranged to analyze the

representation of the breath analysis and compare with at least one predetermined value of an intoxicating substance, and if the predetermined value is exceeded activate the communication unit (13) to issue an alarm.

7. The personal protection device (1, 101, 201) according to any of the preceding claims, wherein the proximity sensor (7, 107) is a ultra-low power proximity sensor.

8. The personal protection device (1, 101, 201) according to claim 6, wherein the ultra- low power proximity sensor (7, 107) is a capacitive or an inductive proximity sensor.

9. The personal protection device (1, 101, 201) according to claim 6, wherein the ultra- low power proximity sensor (7, 107) is a mechanical switch.

10. The personal protection device (1, 101, 201) according to any of the preceding claims, further comprising at least one second sensor arranged to detect a condition associated to the usage of the helmet (1), and the control and computational unit (12) being operable in a low power stand-by mode monitoring an input from the proximity sensor (7, 107) and the at least one second sensor; and upon input from the proximity sensor proximity sensor and the second sensor activate the breath analyzer.

11. The personal protection device (1, 101, 201) according to claim 9, wherein the at least second sensor is a switch detecting the position of a visor (2).

12. The personal protection device (1, 101, 201) according to any of the preceding claims, wherein the said breath analyzing system is encased and provided with protective material.

13. The personal protection device (1, 101, 201) according to any of the preceding claims, wherein said breath analysis includes the computation of the difference between maximal and minimal readings during a breath cycle of a substance and a tracer signal, said tracer signal representing the concentration of carbon dioxider

14. The personal protection device (1, 101, 201) according to claim 1, wherein said

transfer from inactive to active mode of operation being further conditioned on the locking of a mechanical mechanism (19, 109) preventing said helmet from being involuntarily removed from said skull by translational or rotational movement.

15. The personal protection device (1, 101, 201) according to any of the preceding claims, wherein the flow control assembly (11) includes flow impedances which are either resistive or capacitive and wherein the resistance is dominated by the air flow through a preheater provided in the flow control assembly (11), the preheater resistance R_h, and the capacitance by the breath analyzer cavity capacitance C_c, and the response time To is determined by the equation To = R_hC_c and wherein the response time To is less than one second, and preferably less than 0.5 second.

16. The personal protection device (1, 101) according to any of claims 1 to 14, wherein the personal protection device (1, 101) is a helmet.

17. The personal protection device (201) according to any of claims 1 to 14, wherein the personal protection device (201) is an attachment configured to be attached to a helmet.

18. The personal protection device (201) according to any of claims 1 to 14, wherein the personal protection device (201) is a collar configured to be attached to a helmet (200).

19. A method of performing breath analysis suitable for drivers of open vehicles by the use of a personal protection device (1, 101, 201) comprising a breath analyzing system (3) comprising a breath analyzer (6, 106, 206), an proximity sensor (7, 107), a control and computational unit (12), a flow control assembly (1 1) and a communication module (13), the method comprising the steps of:

- (805) keeping the breath analyzing system in an inactive mode wherein only the proximity sensor (7, 107) is actively in a detecting mode;

- (810) turning, if at least the proximity sensor (7, 107) indicates that the personal protection device (1, 101, 201) is worn by a user, the breath analyzing system (3) from an inactive mode into an active mode, and if not, the breath system remains in inactive mode;

- (815) the control and computational unit (12), in the active mode, activating the breath analyzer (6, 106, 206) and the active element (11a, 211a) of the flow control assembly (11), the breath analyzer (6, 106, 206) in response outputs a representation of measured data to the control and computational unit (12);

- (820) the representation of measured data is analyzed by the control and

computational unit (12);

- (825-840) if the estimated breath concentration of a selected intoxicating substance exceeds a predetermined value, at least an alarm is activated (830), and if the estimated breath concentration of the intoxicating substance is lower than the predetermined value, the system returns to an inactive mode (835).

20. The method according to claim 18, wherein the step of turning the breath analyzing system (3) from an inactive mode to an active mode (810) further comprises receiving and analyzing the input from a plurality of sensors or indicators and only if the input from the plurality of sensors or indicators corresponds to a predetermined scheme turn the breath analyzing system (3) from the inactive mode to the active mode.

21. The method according to claim 19, wherein the personal protection device (1, 101, 201) is a helmet and the predetermined scheme comprises the visor (2) of the helmet (1) being in a closed position.

22. The method according to claim 20, wherein in the step of activating the breath

analyzer (815), comprises a pre-step of activating the active element (11a, 211a) of the flow control assembly (11) before activation of to give a stable flow of air, including expiratory air, through the breath analyzer (815).

23. The method according to any of claims 18 to 21, wherein in the air transport from the users mouth/nose to the breath analyzer (815) is effectuated with a time delay considerably shorter than one second.

24. The method according to any of claims 18 to 22, further comprising a step of

immobilizing (831) the open vehicle if the estimated breath concentration of a selected intoxicating substance exceeds a predetermined value (825).

25. The method according to any of claims 18 to 23, wherein said breath analysis includes the computation of the difference between maximal and minimal readings during a breath cycle of a substance and a tracer signal, said tracer signal representing the concentration of carbon dioxide.

26. The method according to any of claims 18 to 24, wherein said transfer from inactive to active mode of operation being further conditioned on the locking of a mechanical mechanism (19, 109) preventing said personal protection device (1, 101, 201) from being involuntarily removed from its correct position on a user by translational or rotational movement.