GB2420616A

GB2420616A - Personal pollution monitor

Info

Publication number: GB2420616A
Application number: GB0425341A
Authority: GB
Inventors: Victor Higgs
Original assignee: Individual
Current assignee: Individual
Priority date: 2004-11-17
Filing date: 2004-11-17
Publication date: 2006-05-31
Anticipated expiration: 2024-11-17
Also published as: GB2420616B; GB0425341D0

Abstract

This invention relates to a personal device for monitoring pollution gases and particulate pollution. This device is designed to alert and warn the user that the local environment is polluted and to take the necessary precautions. This present invention relates to a personal, portable, handheld and wearable detector system. The pollution monitor in one embodiment includes a particulate sensor and a chemical sensor or sensor array for detecting pollution gases. The sensor outputs are analyzed by a microprocessor and if the pollution levels are higher than the set thresholds this will warn the user by an audible and visible alarm. The alarm signal can also be output via a communications module to a local network via a wireless link. This system will have a low operating power and a compact small size to facilitate its function as a personal pollution monitor.

Description

1 2420616 Personal Pollution Monitor As many cities around the world

become more congested, concerns over the level of urban air pollution being generated and in particular its impact on localized human health effects such as asthma or bronchitis. Human beings breathe in the ambient air eveiy few seconds and therefore the urban air pollution is therefore one of the most important environmental issues that may be considered due to its direct effect on human health. The primary airborne pollutants covered are gaseous sulphur dioxide (SO2), nitrogen oxides (NOX, NO/NO2), benzene, ozone, carbon monoxide and carbon dioxide (CO and C02), volatile organic compounds (VOCs) and particulate matter (PM10 and PM2.5).

In both developed and new industrialized countries, the major air pollution problem has been high levels of smoke and sulphur dioxide arising from the combustion of sulphur-containing fossil fuels such as coal for domestic and industrial purpose. The major threat today to clean air is now related to traffic emissions. Petrol and diesel-engine motor vehicles emit a wide variety of pollutants, principally CO, oxides of nitrogen (NOx), VOCs and particulates (PM10), which have an increasing impact on urban air quality. CO is a toxic gas which is emitted into the atmosphere as a result of combustion processes, and is also formed by the oxidation of hydrocarbons and other organic compounds. In European urban areas, CO is produced almost entirely (90%) from road traffic emissions. Nitrogen oxides are formed during high temperature combustion processes from the oxidation of nitrogen in the air or fuel. The principal source of nitrogen oxides - nitric oxide (NO) and nitrogen dioxide (NO2), collectively known as NOx - is road traffic, which is responsible for approximately half the emissions in Europe. NO and NO2 concentrations are therefore greatest in urban areas where traffic is heaviest. The principal source of this gas is power stations burning fossil fuels which contain sulphur. Major SO2 problems now only tend to occur in cities in which coal is still widely used for domestic heating, in industry and in power stations. As many power stations are now located away from urban areas, SO2 emissions may affect air quality in both rural and urban areas. Even moderate concentrations may result in a fall in lung function in asthmatics. Tightness in the chest and coughing occur at high levels, and lung function of asthmatics may be impaired to the extent that medical help is required. Sulphur dioxide pollution is considered more harmful when particulate and other pollution concentrations are high. This gas prevents the normal transport of oxygen by the blood. This can lead to a significant reduction in the supply of oxygen to the heart, * 2 particularly in people suffering from heart disease. Nitrogen dioxide can irritate the lungs and lower resistance to respiratory infections such as influenza. Continued or frequent exposure to higher concentrations than those normally found in the ambient air may cause increased incidence of acute respiratory illness in children and adults.

Airborne particulate matter varies widely in its physical and chemical composition, source and particle size. PM10 particles (the fraction of particulates in air of very small size (<10 jim)) are of major current concern, as they are small enough to penetrate deep into the lungs and so potentially pose significant health risks. Larger particles meanwhile, are not readily inhaled, and are removed relatively efficiently from the air by sedimentation. The principal source of airborne PM10 matter in European cities is road traffic emissions, particularly from diesel vehicles.

Particulate matter causes inflammation of the airways which may lead to worsening of existing lung disease and enhance the sensitivity to allergens of people with hay fever and asthma. It may also have the ability to alter the ability of blood to clot and circulating red cells and platelets, a mechanism that could explain the adverse influence of inhaled particles on cardiovascular morbidity (illness) and mortality (death).

The potential for particles to cause health effects is related to their size. Particles up to 100 jim enter the body during breathing, but it is only the very small particles, below about 5 jim aerodynamic diameter that can reach deep into the lung. It is widely accepted that it is these very small particles that have the main potential for causing health effects. It is therefore very important to define the size of the particles that are to be measured. The current focus of health- related sampling of particulate matter is on PM10, however there is also a growing interest in monitoring finer fraction of particles, such as PM2. 5. Road transport is a significant source of primary particulate matter emissions, especially in urban areas. In the UK it accounts for about a third of emissions of PM10; in London this rises to over 80%.

Exposure to ambient air Pollution may be deleterious to the health of children and adults with asthma. Some children with asthma (as well as some children without asthma) have decreases in lung function after exposure to a pollutant that is formed primarily by vehicular exhaust and is the principal component of urban smog, is associated with asthma exacerbations in some children with reactive airway disease. Exposure to ambient sulfur oxides and suspended particulates may also lead to pulmonary function decreases in adults and children. Nitrogen dioxide is an oxidant gas that can penetrate deep into the lungs and damage delicate lung tissues.

Some studies have shown a relationship between nitrogen dioxide and respiratory symptoms.

Some further research has demonstrated that the prevalence of bronchitis, wheezing, and asthma increased with each increase of 10 parts per billion (ppb) in indoor nitrogen dioxide concentrations. Epidemiologic studies have documented that the relationship between air pollution and hospital admissions for respiratory illnesses may be the largest among people in inner cities. It has been demonstrated that the average number of emergency department visits for asthma or reactive airways disease among inner-city children was 37%.

It has been found in many parts of the developed world that both pollution gases and particulate pollution are detrimental to human health. In addition, people already suffering respiratory illness such as asthma could have breathing difficulties or suffer an asthma attack if they enter an area which is heavily polluted. Air pollution studies on the London underground have shown that the particulate pollution levels are 73 times higher than a street level and a 20 minute journey on the underground had the same effect as smoking a cigarette.

There are 300 million asthma sufferers in the world and that figure is expected to jump to 400 million in 20 years. Asthma is now one of the world's most common long-term conditions, according to figures released during the World Asthma Meeting in 1 in 20 people, approximately 5% of the world's Population struggle with Asthma. The report indicated that the rate of astluna increases as communities adopt western lifestyles and become urbanized.

8 million people in the UK have been diagnosed with asthma and 5.1 million people in the UK are currently receiving treatment for asthma: 1. 4 million children (1 in 8) and 3.7 million adults (1 in 13). On average, 1,400 people die from asthma each year in the UK. An estimated 75% of hospital admissions for asthma are avoidable and as many as 90% of the deaths from asthma are preventable. Respiratory disease is the most common illness responsible for an emergency admission to hospital and Asthma now costs the UK National Health Service on average 850 million per year.

There is a need to have personal pollution monitor to alarm or warn the user that they are entering a polluted area and they need to preventive action (leave the area or take the necessary medicine or wear a face mask) .

Gas sensors are available to detect pollution gases, solid state detectors based on, semi conducting metal oxide, Metal oxide field effective transistors and electrochemical cells have been widely used to measure air quality and commercial systems are readily available for numerous gas-phase species, including carbon monoxide, nitrogen dioxide, ozone, sulphur dioxide, and volatile chlorides and hydrocarbons. Microcalorimetric gas sensors (pellistors) burn combustible gases with the surrounding air on the surface of a small ball or film of a catalytically active metal. The typical catalyst, e.g. Pt, Pd or Rh, is kept at 500-600 C. The heat of combustion in the presence of a gas is balanced by a reduction in electrical heating power. The power consumption serves as the signal, indicating the concentration of flammable gases. This type of sensor is the current standard for the detection of explosives in plants, because it shows a higher accuracy and long-term stability than the oxide containing sensor prevailing in home applications for the same purpose. Electrochemical gas cells ionize the gas molecule at a three- phase boundary layer (atmosphere, electrode of a catalytically active material, electrolyte). Some examples of electrode materials are platinum for CO, gold for NO2, and activated coal for SO2 detection. The ion current through the electrolyte to the counter electrode serves as the signal in amperometric-type cells. The chemical-resistor is, (typically based on metal oxides) for reasons of its simplicity, perhaps the most attractive chemical sensor type for portable applications. The conductivity (resistance) of the chemical-resistor is proportional to the analyte concentration in the ambient environment. These can be based on tin oxide or mixed metal oxides.

Particulate contamination can be detected using a number of different techniques. Gravimetric cumulative samplers, collect PM10 particles deposited on a filter over a sampling period of normally 24 hours. The mass of particles collected on the filters is determined by weighing.

Using direct reading instruments, sampling and analysis is carried out within the instrument, and the concentration can be obtained almost immediately. Optical particle counters employ the interaction between airborne particles and visible light in a sensing region, and generally their response is dependent upon the size distribution, shape and refractive index of the particles.

They therefore require calibration to give results in terms of mass or number concentrations.

This calibration only holds provided that the nature of the particles does not change and hence measurements obtained in ambient air are open to considerable uncertainty. Oscillating Microbalance such as the Tapered Element Oscillating Microbalance (TEOM), measure the frequency of mechanical oscillation of an element such as a tapered glass tube is directly proportional to the mass of the tube. Change in effective mass of the tube, such as that due to deposition of particles on the surface of a filter at the free end of the tube, is reflected in a change in its resonant frequency.

Although most pollution sensors and particulate sensors have high sensitivity and accuracy they are more suitable for dedicated use in a local area and not generally portable or for personal use.

These devices can be physically large and cumbersome and usually require high electrical power consumption and an expert user.

People suffering from broncal or asthma conditions will benefit greatly from a personal portable pollution monitor, to detect local polluted environments and to act as an early warning system.

This will allow the user to take preventive action, to leave the local area or take alternative precautions (take medication or wear a face mask) . Such a system could be configured to have additional benefits for military personal entering into hostile environments, or policeman, or ambulance, health or public workers entering into an unknown local area after an accident has taken place.

This application is focused on a device that monitors pollution gases and particulate matter. This system would be portable, handheld and wearable, and indicate alarm or warn the user that the local environment is polluted.

Statement of invention

The present invention provides a system to measure both pollution gases and particulate contamination in the same device. The present invention also provides the user with a personal, portable and wearable detector system. These devices according to certain aspects of the present invention will be advantageous due to their lower power consumption and be wearable, and designed to detect and indicate to the user that the environment is polluted. This system will act as an early warning device indicating to the user that the pollution levels in their current local environment is at a level that could cause them some discomfort or even lead to them suffering breathing problems. This is particularly relevant to people suffering from respiratory or bronchial or asthma conditions, and the user needs to take the necessary precautions. This could mean leaving the current area, or entail taking the necessary medicine or wearing a face mask.

The personal pollution monitor will include a particulate sensor, separate chemical sensors or a chemical sensor array, a microprocessor and digital electronics for signal conditioning and processing. The sensor array or sensors will have the capability of detecting individual gases, for example NOx, SO2 and or CO and or monitoring temperature and humidity. The device will be battery operated and could have the capability of storing data and or transmitting data via wireless, infrared to a remote network or computer.

Description of the Drawings

The invention will now be described solely by way of example and with reference to the accompanying drawings in which Figure 1 illustrates a block diagram of a personal pollution monitor in accordance with an exemplary embodiment of the invention.

Figure 2 illustrates a configuration diagram of a personal pollution monitor in accordance with an exemplary embodiment of the invention.

Detailed Description of the Invention

The present invention is described hereinafter with reference to Figures 1-2. The personal pollution monitor (see Figures 1-2) of the present invention comprises a device housing I which forms a contained area for the monitoring the ambient air flow at the detection zone 2. The device contains two functional detection systems, one for particle detection and the other for pollution gas detection. The illuminating portion for particle detection contains a control and driver 3 for the light source 4, (preferably a LED or laser diode). The light beam source generates a beam for illuminating the airborne particles within the detection area. This source could be randomly polarized or polarized in a specific direction (perpendicular to the plane of the optical axis or parallel) and then unfocused or focused into the detection zone using the excitation optics 5 (focusing lens and or polarizer). The scattered light produced by the airborne particles is directed onto the collection optics 6 (focusing lens and or de-polarizer) preferably aligned at an angle of 600 to the incident optical axis. The intensity of the scattered light is measured using a detector 7. This detector could be a photodiode, photomultiplier or a linear or 2D array detector.

As shown in Figure 1, the detector photoelectric current is fed into a current-voltage converter 8, amplified, and signal processed 9. The voltage signal is converted into a digital signal (A/D converter 10) and fed into a microprocessor 11 for computing the concentration of particles. If the concentration of particulates is above a threshold limit the microprocessor will output signals to change the LED (12) signal from green to red indicating the local area is polluted. In parallel an audible and or vibrating alann (13) could also be activated if the local area is polluted. The system is powered by a rechargeable battery 14.

The utilization of polarized excited light will lead to more information on the shape of the particle and type of particle. For vertically polarized excitation light detectors placed in the vertical plane will respond mainly vertically scattered light. Additional detectors placed in the horizontal plane will detect out plane light. These detectors could be either single element photodetectors with the appropriate collection optics or array detectors.

Additional analysis of the pollution particles could be differentiated by using fluorescence.

Biological aerosols like pollen or bacteria could be differentiated from non-biological particles such as dust. Organic biological materials illuminated by UV light give fluorescence information in the 400-700 nm range. Utilizing a UV light source (e.g. LED or laser diode) and array or single element detectors potential information on particles fluorescence could be obtained. The sensitivity of this type of measurement could be enhanced utilizing additional optics to collect light over a wider angle of emission, using ellipsoidal or parabolic mirrors.

Utilizing a UV light source (LED or laser diode) for optical excitation component of the particle detection, will enable the detection of smaller particles. A second benefit could be utilizing the UV excitation light source to activate the sensitivity of the chemical sensors or sensor arrays to particular pollutant gases. Also the UV light source could be used to facilitate the desorption of pollutant gases already absorbed on the surface of the chemical sensors at room temperature.

Such gases would be normally desorbed by increasing the operating temperature of the device.

It should be emphasized that that although the detector and collection optics were each aligned in the forward scattering direction at an angle of 600 to the incident optical axis, it is not essential to this invention for the angle to be limited to a 60 and any angle within a range of 0 90 may be used.

The pollution monitor also comprises a directional sampling port. This located at the bottom of the shielding housing to direct sampling air drawn from the atmosphere by a small heated plate or small fan 15.

The communication module 16, can transmit the data from the chemical sensors or sensor array and the particulate monitor in a number of ways depending on its configuration. It could contain a connector for data output via a serial link RS-232, RS-485 port or a USB port. Alternatively the output signal could be wireless transmitted through radio frequency (RF) unit or an infrared unit. The status of the local area is measured and tested and could be monitored and if the threshold level is above the set threshold the user is warned and the coloured LED's and or the audible and or vibrating alarm will be activated. The alarm status could be transmitted to a local area network. This would act as a back-up precaution just in case the polluted area has reached hazardous levels.

The apparatus would have a mechanism to attach it to your clothes, a clip or alternatively a strap or holder.

An alternative particulate based measurement could be carried out using an oscillating sensor element, whose resonant frequency changes when particulates are adsorbed on its surface. The particulates would affect the resonant frequency. This type of sensor could be used in conjunction with high frequency operated acoustic wave chemical sensors.

The sensor elements 17 for the pollution sensors could be a based on the following types of sensor, a gas field effective transistor (FET), surface and or bulk acoustic wave devices or chemical-resistor sensors or electrochemical cells or an optical method based on surface plasmon resonance or measuring gold particle plasmon absorption changes on gas adsorption. The Gas- FET contains an FET with a gate metallization exposed to the surrounding atmosphere. When a gas is absorbed on the on the surface protons can diffuse to the metal gas interface. This results in a dipole layer which affects the threshold voltage of the device. By measuring the drain current is the sensor signal used for detecting the adsorbed gas. Surface and bulk acoustic wave devices detect a mass change of an adsorptive layer. The simplest device utilizes a piezoelectric quartz disc oscillator. The frequency shift is directly related to the amount of absorbed mass.

Thereby coating the quartz disc with e.g. a polymer absorbing the gas of interest can de detected.

Higher frequencies are attainable using surface acoustic wave (SAW) devices which are more sensitive. Electrochemical cells could be also utilized to detect pollution gases. The surface plasmon resonance technique is sensitive to small changes in refractive index at a metaldielectric interface, and can be readily miniaturized and has low power consumption. Chemical sensors containing gold particles could be monitored for changes in the gold plasmon absorption region. These optical techniques could be more closely incorporated with the optical light source arrangement used in detection of pollution particulates.

One simple implementation method is to use individual chemical sensors (17) for the pollutant gases or a sensor array (17) based on chemicalresistors. This type of sensor works by heating the material in air, whereby they become covered in layers of absorbed oxygen. This produces a large change in the resistance of the semiconductor element. When the sensor comes into contact with other gas pollutants these molecules can also be absorbed on the surface and thereby transfer electrons between the adsorbed gas molecule and the sensor surface. This can cause a change in the conduction typically an increased conductivity. An electrical circuit 9 is required to convert the change in resistance to an electrical output, which corresponds to the amount of gas absorbed. This circuit supplies a constant current to the sensor resistive load, the voltage measured across the load determines the load resistance which corresponds to the amount of pollution gas adsorbed. This information is feed into A/D converter 10 and then the microprocessor 11 which is used to determine if the exposed pollution gas is above the acceptable threshold limits. If the local area is polluted then the LED alarm 12 and audible or vibrating alarms 13 are activated.

Recent advances in nanotechnology can greatly improve the sensor performance due to the possibility of modifying the microstructure and chemistry at the nanometre scale, thus enhancing the chemical interaction. Nanometre structured materials, with small grain size, large number of grain boundaries and high specific area present new opportunities for the development of the next generation of gas sensors for air quality monitoring and control with significantly unproved performance.

The chemical-resistors could be made from appropriate nanometre-sized materials, this type of material would be more sensitive and specific the conventional sensor materials. They could also offer the possibility of room temperature operation. This would reduce power consumption and facilitate the operation of a battery powered personal device. One material that is suitable for use in this invention is carbon nanotubes. There has been some research work showing the potential of carbon nanotubes to act as chemical sensors. Individual nanotubes are manipulated across to conducting electrodes, and a simple electronic device is produced. Due to the variability of manufacturing individual tubes carbon nanotubes can have quite different chemical and physical properties. However, if a large density of nanotubes were incorporated into a sensor element, and they were additionally functionalized to enhance sensitivity, this would overcome the issues with using devices based on individual nanotubes. In addition, this would also make it easier to manufacture without the complications of manipulation and the precise movement required creating a single device.

Another class of materials suitable would be nanometre controlled metal oxide materials doped with noble metals, Ag, Pt, Pd and Au. The controlled growth of their microstructure and morphology, such as grain size and particle size leading to higher surface area and reactivity would be beneficial in terms of improving performance.

Another example would be to use gold doped metal oxide catalysts supports for chemical resistors. Previous work has shown that gold-doped catalyst supports were very active for room temperature oxidation of CO and for a number of other chemical reactions. The precipitation methods for the catalyst preparation result in small metallic gold particles uniformly dispersed on the support. The best results are obtained when these particles are less than 5 nm in diameter, so that there is sufficient chemical interaction between the metal and the support. Utilizing the appropriate metal support and the nanometre size gold particles different sensor elements could be prepared. These gold doped materials could also be used as optical sensors; it has been observed previously that gas absorption can modi!' the gold plasmon absorption band.

Another type of material that could be used is Ti02 in the form of nanocrystallites or nanotubes.

This material could be enhanced by illuminating the sensor system to UV light irradiation. The structural and morphological properties as well as UV irradiation could modif' the influence of the properties of hO2 sensor. The photocatalytic activity would enhance the sensitivity of the nanosized hO2 material and doping with noble metal dopants especially gold could offer enhanced sensitivity. The UV light could be directed from the particle detection module onto the chemical sensor.

Another material that could be used to make chemical-resistors is carbon black or conducting polymers or composite polymers. Exposure to particular gases causes the sensors to swell, which increases the electrical resistance. Simply employing different polymers a number of different tuned sensors could be fabricated and selective to the pollution gases.

An alternative class of materials is nanostructured systems, mesoporous materials, which are characterized by nanometre-sized cavities or pores. These materials offer the ability to process nanoporous materials with greater control in compositional and pore structure variation will open offer for improved performance for chemical sensor. New organometallic compounds have been used as a precursor design to create transition metal oxides with a hexagonally packed cylindrical mesoporous structure. These materials are characterized by uniform pore diameters of 2-10 nm with surface areas of excess of 600 m2/g and pore sizes. Similar structures could be formed on alumina or silica based structures. All these porous materials could be readily doped and sensitized using both inorganic and organic dopants distributed in the porous structure.

An alternative method for fabricating the chemical-resistors would be to create and array of pollution gas sensors, rather than using individual gas sensor elements. The individual sensors allow only one type of gas to be detected rather than a mixture. The array would be composed of fmite number of individual sensor elements, combined to form the array element. To reduce power consumption a micro-design and semiconductor fabrication route is desirable and the high level of integration in such an array would improve manufacturing costs and improve sensitivity to gas mixtures. These sensor elements could be based on any of the materials discussed in this section.

Claims

Claims 1. A personal pollution unit for monitoring local air quality

comprising a plurality of sensors measuring and specific parameter of the air quality and a microprocessor for signal analysis received from the sensors and producing an output signal.
2. A pollution monitoring unit according to claim 1, comprising of individual gas sensors or a sensor array and a particulate sensor monitoring the air and a microprocessor for signal analysis received from the sensors and producing an output signal.
3. A pollution monitoring unit according to claim 1, the gas sensors or sensor array is selected from the group of, Gas-FET, surface or bulk acoustic wave device, chemical resistor type, electrochemical cell or an optical sensor based on plasmon absorption or surface plasmon resonance.
4. A pollution monitoring unit according to claim 1, the gas sensors or sensor array wherein the sensor element is selected from the following group consisting of a conducting polymer or composite polymers, carbon nanotubes, titania nanotubes or nanocrystallite material, semiconductor oxide with nanometre sized structure, gold doped metal oxide catalysts supports and mesoporous materials such transition metal oxides, alumina or silica.
5. A pollution monitoring unit according to claim 1, the particulate sensor wherein the sensor uses one of the following or a combination, a light scattering mode with un-polarized light, a light scattering mode with polarized light, a fluorescence method and a vibrating oscillating transducer.
6. A pollution monitoring unit according to claim 1, in which a UV light source (LED or laser diode) is used to activate and enhance the sensitivity of the gas sensor or sensor array, and to be used to illuminate the particulate pollution for particulate detection.
7. The apparatus described in claim 1, including a communication module to provide an output signal to an external network.
8. The apparatus described in claim 7, wherein the communication module includes a wireless interface and a physical bus interface.
9. The apparatus described in claim 1, additionally including a communication module to the user indicating that the sensor output signal has a level above the acceptable threshold value.
10. The apparatus of claim 9, wherein the communication module includes a visible LED indicator, a vibrating or audible alarm.
11. The apparatus of claim 8, wherein the wireless module has includes a RF or IR Communication link.
12. The apparatus of claim 8, wherein the physical bus interface has a serial RS-232, RS-485 or a USB port.
13. The apparatus of claim 1, would have a mechanism to attach it to your clothes so that it could be wearable.
14. The apparatus of claim 8, would have a mechanism to attach it to your clothes so that it could be wearable.
15. A pollution monitoring unit according to claim 2, the gas sensors or sensor array is selected from the group of, Gas-FET, surface or bulk acoustic wave device, chemical resistor type, electrochemical cell or an optical sensor based on plasmon absorption or surface plasmon resonance.
16. A pollution monitoring unit according to claim 2, the gas sensors or sensor array wherein the sensor element is selected from the following group consisting of a conducting polymer or composite polymers, carbon nanotubes, titania nanotubes or nanocrystallite material, semiconductor oxide with nanometre sized structure, gold doped metal oxide catalysts supports and mesoporous materials such transition metal oxides, alumina or silica.
17. A pollution monitoring unit according to claim 2, the particulate sensor wherein the sensor uses one of the following or a combination, a light scattering mode with un-polarized light, a light scattering mode with polarized light, a fluorescence method and a vibrating oscillating transducer.
18. A pollution monitoring unit according to claim 2, in which a UV light source (LED or laser diode) is used to activate and enhance the sensitivity of the gas sensor or sensor array, and to be used to illuminate the particulate pollution for particulate detection.
19. The apparatus described in claim 2, including a communication module to provide an output signal to an external network.
20. The apparatus described in claim 19, wherein the communication module includes a wireless interface and a physical bus interface.
21. The apparatus described in claim 2, additionally including a communication module to the user indicating that the sensor output signal has a level above the acceptable threshold value.
22. The apparatus of claim 21, wherein the communication module includes a visible LED indicator, a vibrating or audible alarm.
23. The apparatus of claim 20, wherein the wireless module has includes a RF or IR communication link.
24. The apparatus of claim 20, wherein the physical bus interface has a serial RS-232, RS-485 or a USB port.
25. The apparatus of claim 2, would have a mechanism to attach it to your clothes so that it could be wearable.
26. The apparatus of claim 20, would have a mechanism to attach it to your clothes so that it could be wearable.