WO1994022686A1

WO1994022686A1 - Breath sensor apparatus

Info

Publication number: WO1994022686A1
Application number: PCT/US1993/011248
Authority: WO
Inventors: John T. Ruocco; Robert B. Whitney; Leon Pasqua; John Shea; Babak Dastgheib-Beheshti
Original assignee: Alcohol Sensors International, Ltd.
Priority date: 1993-04-01
Filing date: 1993-11-19
Publication date: 1994-10-13
Also published as: AU5613894A

Abstract

An apparatus for monitoring the alcohol level of an individual's breath allows a motor vehicle or other equipment to be operated only when the alcohol level is below a predetermined value. In addition to breath alcohol, the temperature and the pressure of the breath sample are also monitored. The outputs of the sensors (TH2, 20, SN1) are passed to a processor (48) which performs the appropriate analysis of the outputs. The processor (48) also controls test timing, allows for storage of test data, and interfaces with the equipment to be controlled. In a preferred embodiment, intended to be utilized in conjunction with vehicle operation, routines are utilized to seek retest on a repeating basis during operation and to insure that the system is not defeated by intentional operator action.

Description

BREATH SENSOR APPARATUS The Present invention relates to a sensor adapted for use in an electronic system for sensing the presence of alcohol in the breath of a human and the electronic system incorporating such a sensor.

Background of the Invention

The cost, in personal injury and property damage, due to accidents involving intoxicated drivers is well documented and represents an acceptable risk to the public. Accordingly, there have been numerous attempts to provide an apparatus which is intended to make a determination of the amount of alcohol consumed by an individual and thus the alcohol level of the blood. The common methodology employed in such apparatus is the use of a sensor adapted to measure the amount of alcohol in a breath sample passed along the sensor. Typically, the apparatus analyzes a breath sample requested from the operator of the motor vehicle prior to engagement of the ignition system. A sensor reading above a predetermined threshold, corresponding to an unacceptable alcohol level, locks out the ignition circuit and prevents starting of the vehicle.

It has been found that improved performance can be obtained by incorporating an alcohol-responsive sensor element into a sensor apparatus which senses other and additional breath characteristics and which permits further and more accurate differentiation between a valid breath sample and a sample derived from another source to be made.

It is accordingly a purpose of the present invention to provide an alcohol monitoring sensor apparatus and system incorporating such a sensor which has an increased resistance to being defeated. A further purpose of the present invention is to provide a breath sensor and associated monitoring apparatus which can accurately differentiate between breath and other gas/vapor sources. Another purpose of the present invention is to provide a sensor apparatus which can detect changes in the alcohol level of a user over a period of time.

A still further purpose of the present invention is to provide a sensor apparatus which may be utilized in a system requiring sampling on a periodic basis to deter the ingestion of alcohol during vehicle operation.

Yet another purpose of the present invention is to provide a sensor which is capable of measuring a plurality of breath characteristics to provide an output which may be processed to determine with high accuracy the existence of a valid breath sample.

Another purpose of the present invention is to provide a system capable of interfacing a breath sensor with a vehicle or other equipment to be controlled. A still further purpose of the present invention is to provide an interface system which can record breath sample readings, as well as associated equipment operating parameters, for later review and analysis. Brief Description of the Invention In accordance with the above and further objects, the present invention comprises a sensor assembly which monitors several aspects of the gas sample provided. In addition to monitoring the alcohol content of the sample, the temperature difference between the sample and ambient air, as well as the relative flow pressure of the breath sample are measured. Each monitored parameter causes an individual output signal to be generated. The combination of outputs generated by the sensor assembly may be inputted into logic circuitry which analyzes the factors to determine whether the gas sample received is in fact a breath sample, or is derived from another source, such as a fan or other surrogate. If a valid breath sample is received, the sample may be further analyzed to determine if the alcohol level thereof is within appropriate guidelines for safe operation of a vehicle. Such analysis can be performed on a repeated basis as may be required to prevent subsequent ingestion of alcohol by the operator. The sensor assembly outputs may be used for other or additional purposes, such as development of an operation log for the vehicle. To further prevent the operator from defeating the system, the control system may provide for repeated testing while the vehicle or other piece of equipment is in operation. In the case of a vehicle, retesting may be performed on either a random or predetermined schedule. By monitoring the operation of the vehicle, additional testing routines may be invoked as may be required to provide further safeguards. These may include additional tests when the vehicle is in an idle condition for an excessive about of time, or retest after ignition restart. Brief Description of the Drawings A fuller understanding of the present invention will be achieved upon consideration of the following detailed description of preferred, but nonetheless illustrative embodiments of the invention when take in conjunction with the annexed drawings, wherein: FIG. 1 is a perspective view of the sensor assembly of the present invention;

FIG. 2 is a sectional view taken along line 2-2 in FIG. 1; FIG. 3 is a detailed representation of the pressure sensing portion thereof; FIG. 4 is a schematic diagram of the circuitry of the sensor assembly;

FIG. 5 is a block diagram of the interconnection between the different functional parts of the invention; FIG. 6 is a flowchart of the processing portion of the invention;

FIG. 7 is a representation of a first alternative pressure sensor; and FIGs 8a and 8b are representations of further alternative pressure sensor embodiments. Detailed Description of the Invention

The present invention is based upon a relationship between the blood alcohol level of an individual and the amount of alcohol vapors appearing on the breath of the individual. In general, a blood alcohol level of approximately .08 to .10 percent is considered to define a level of intoxication sufficient for a charge of "DWI" or driving while under the influence of alcohol to be assessed against a driver. Because the temptation to trick a sensor unit measuring only alcohol level is great, especially when the sensor is intended to be utilized in a situation not monitored by an independent validator, the present invention includes safeguards to minimize the ability of the user to supply a surrogate breath which would provide an erroneous measure of the user's alcohol level.

The present invention compares the blood alcohol level, as represented by the level of breath alcohol, to a value below the danger range, typically about .03 percent. Sensing is preferably accomplished by a semiconductor element, preferably the TGS 823 Gas Sensor marketed by Figaro Engineering, Inc. of Osaka, Japan. The TGS sensor is a bulk semiconductor formed from sintered tin dioxide. When the sensor is heated to a high temperature (about 400°C) oxygen in clean air is adsorbed onto its surface, providing a potential barrier which raises the resistance of the sensor. When the sensor is exposed to a reducing atmosphere, such as ethanol vapors, the surface adsorbs the molecules which are oxidized by the trapped oxygen. This lowers the potential barrier, reducing the sensor resistance. The degree of resistance change is proportional to the amount of vapor present.

In the present invention, the alcohol sensor is incorporated into a circuit wherein the resistance change of the sensor results in a variable output voltage, the voltage of the sensor increasing as the resistance decreases. The output voltage registered by the sensing of a non-alcohol-laden breath will never rise above the threshold level defined for an alcohol-laden breath. The sensing circuitry relies upon a fixed value threshold for a pass/fail determination. Because of the stability of the sensor, however, the output voltage can additionally be used for quantitative measurement, as well as qualitative.

As depicted in the sensor apparatus circuit 10 shown in FIG. 4, the voltage developed across the active terminals of the TGS sensor SNl is connected to the inverting input of operational amplifier U1B, configured as a differentiator. The output of the differentiator at pin 7 produces sharply-defined leading and tailing edges corresponding to the beginning and end of the breath. The use of the differentiator circuit allows precise identification of the start and end of the breath so that the sensing and analysis circuitry can be properly energized. The differentiator may be temperature compensated by use of TH1. A heater is an integral part of the sensor. This allows the sensor to exhibit constant response over a wide range of ambient conditions. As shown, an output voltage of approximately .3 volts is applied to the input of U1B when no breath is present. A typical composition of alcohol-free human breath raises the output to between .4 and .5 volts, while a blood alcohol level of .03 percent or higher causes a rise to 1.5 volts and above. With the specified sensor SNl, a valid breath sample may cause a slight dip below the ambient output voltage upon breath commencement, followed by a rise above ambient. A surrogate breath, or a breath of large volume and pressure, beyond the flow parameters intended for proper analysis, can drive the initial response substantially below ambient prior to any increase. This different response may be measured by the processing circuitry and can be used as part of the breath verification procedure. In addition to monitoring the alcohol content of the breath, the sensor assembly includes additional monitoring sub-system portions. Thus, temperature-responsive resistors TH2 and TH3 are positioned within the sensor housing so as to be separately responsive to the temperature of the "breath" directed into the housing and the ambient temperature of the housing at a point displaced from the breath flow path. Each of the temperature- responsive resistors forms a part of a voltage divider bridge network between V_fg and ground, the voltage component being developed across each of the resistors being coupled to the inputs to operational amplifier U1A configured as a comparator. Bridge balance may be adjusted by VR2. As shown, the comparator provides an output at pin 1 when the voltages to its inputs are unbalanced, resulting from the unequal temperatures sensed by the resistors. The voltage is proportional to the temperature difference. Thus, the resistors insure that a breath, which is typically above ambient, is supplied to the sensor, rather than a sample derived from the ambient atmosphere, typically at the same temperature as the sensor interior.

In addition to systems for monitoring the alcohol content and temperature of the breath sample, the sensor assembly also contains a sub-system to monitor the relative pressure of the incoming breath flow. As best seen in FIG. 2, a first embodiment of this sub-system may comprise an optical emitter/sensor element IR1, having light source 12 and sensor 14 on the top surface 16 of head 20. Without an object in front of the source to reflect light to the sensor, the sensor leads 22, 24 indicate an open circuit between them. With reflection of light, however, a closed circuit condition develops. Banner or flutter element 18 is mounted to the side of the head 20, whereby it extends within the path of breath flow. The banner is constructed to be flexibly responsive to low gas flow rates such that, at a zero or low flow rate, the light from the source 12 is not reflected by the banner to the sensor 14. As the flow rate increases, however, the banner increasingly deviates from its at-rest position, fluttering above the source and sensor and providing a reflection for the sensor. The output of the sensor at leads 22, 24 is monitored to detect such reflection, while the source is illuminated by power applied to its leads 26, 28.

In a presently preferred embodiment, the pressure sensor sub¬ system comprises an Omron EE85 photosensor assembly as IR1. The banner 18 may be a small piece of thin gauge latex rubber, one end of which is affixed to the head by adhesive bonding. To improve the reflection efficiency of the banner, it may be white or another light color. In addition, as shown in the figure, it may be formed into an arc in plan, curving away from the sensor head. This bias provides additional rigidity to the banner, minimizing false readings and making the sensor less sensitive to varying orientations of the housing.

Because the user of the sensor apparatus is instructed to blow into the housing with the mouth fully open, the breath gust formed is of low pressure. Depending on the precise structure of the banner, its response may be chosen to provide no flexure, or preferably a slight ripple, causing a weak pulsed response of the sensor to occur during its duration. A greater flow rate, typically evidence of a bogus breath, results in excessive flutter of the banner, causing a corresponding more constant output, which may be sensed and differentiated from a valid breath sample by appropriate processing and logic circuitry. When a low flow (but not zero) output is intended to indicate a valid breath sample, a lack of flutter can be used to indicate that the user is not holding the apparatus at the proper proximity for a proper reading. Thus, the presence of the pressure pulse, as well as its duration and magnitude can be utilized for breath verification.

In a second embodiment, depicted in FIG. 7, the pressure sensor may comprise a rotating structure 126 mounted for rotation as a result of an impinging airflow. As shown therein, cylinder 122 is rotatable on or about axle 124, which may be supported by an appropriate bracket (not shown). The cylinder is provided with a airflow-responsive drive means, which may comprise a plurality of fins or vanes 128. The cylinder body is further provided with light reflection means, such as reflective strips 130, which may be positioned between the vanes to direct the light form source 12 to sensor 14. Rotation of the unit causes a train of reflection pulses to be generated, which is sensed and processed to determine whether a valid breath flow is occurring. A lack of a pulse train indicates that no breath flow exists, while the repetition rate of a created pulse train is indicative of the speed of rotation of the cylinder and thus the airflow velocity. An excessive velocity indicates an invalid or surrogate breath. In addition, the duration of the pulse train can be monitored to determine the breath length and insure that a breath of sufficient length is provided to the alcohol sensor.

Alternatively, one or more vanes, as opposed to portions of the cylinder surface, may be made reflective. Appropriate positioning of the cylinder and sensor with respect to the airflow, as will be recognized by those skilled in the art, can be accomplished to provide optimum response.

It is contemplated that the precise shape of the spinner can be varied. In addition to the "paddlewheel" shape of FIG. 7, a "pinwheel" shape 134, as depicted in FIG. 8a, or a "propeller" shape 136, as depicted in FIG 8b, are alternative structures, in which the reflective surfaces 138 can be created by one or more portions of the fins or arms 140. The sensor assembly circuitry may be preferably mounted in a small enclosure dimensioned to be hand-held. As shown in FIGs. 1 and 2, case 34 in a preferred embodiment may be in the general form of a trapezoidal prism approximately 2 1/2 inches wide x 4 inches long x 1 1/2 inches deep. The components are mounted on a printed circuit board 30 mounted in a known manner within the case. The front face 32 of the case is provided with an elliptical entryway 36 for the breath sample, the rear face 38 of the case being provided with a smaller exit 40. An internal wall 42 may extend from the surface of the printed circuit board to the opposite case inner surface to define an interior passageway through the case for the breath flow.

The gas sensor SNl is mounted generally equidistant between the front and rear faces, its sensing surface extending into the path of the breath within the passageway. The pressure gauge IR1 assembly is mounted slightly offset from the gas sensor, proximate the entryway 36, the banner 18 extending from the edge of the assembly closest to the case front face such that a breath sample bends the banner inwardly, reflecting emitted light to the sensor portion. The emitter/sensor element IR1 is positioned within the darken interior of the case in a manner to minimize the reception of ambient light entering the case by the sensor portion 14.

Temperature-responsive resistor TH2 is positioned proximate the gas and pressure sensors within the breath flow, while reference temperature-responsive resistor TH3 is positioned on the opposite side of wall 42 shielded from the breath flow so as to provide a proper reference signal. A multiconductor cable 44 may extend from the case rear face, and is provided with an appropriate connector to mate with jack Pl on the circuit board to allow each of the signals developed by the sensing sub-systems to be passed to the analysis circuitry and to provide power to the sensor assembly. The outputs of all three sensor sub-systems may be fed to an appropriate analysis means, such as a microprocessor-driven computation and control system. All three test elements - pressure, temperature difference and a positive alcohol sensor output (above quiescent) must be within proper limits to provide acknowledgement that a valid breath sample has been received. Such a determination allows the actual level of the alcohol sensor output to be compared to a reference. It is only when that comparison is performed and the output falls within the appropriate guidelines that a "clear" signal is generated, confirming that a valid breath sample with a passing alcohol level has been received. The clear signal allows the vehicle ignition to be energized and/or other appropriate messages and functions to be performed. The failure of the input breath sample to meet one or more criteria results in a fail signal being generated, which may be used to shut down the monitored system, activate warning indicators and the like, and/or provide a permanent record of the failure. Provision may be further provided to allow one or more retests in a given period before system shutdown occurs. In order to further improve the accuracy of the test procedure, the actual output voltage of the TGS sensor may be sensed on a periodic basis during the period that a valid breath is received. Individual comparisons can be made between such output and stored references, with appropriate calculations being made to wait the results of such comparisons as may be appropriate to enhance the validity of the test. Such statistically-based procedures are well known to those in the art. In order to maintain system accuracy, known alcohol concentrations may be passed over the sensor (with the pressure and temperature sub- systems disabled) and the outputs resulting therefrom being stored by the processing system. FIG. 5 depicts the interconnection of the major operating elements of the apparatus of the present invention with the controlled equipment. In a preferred embodiment, the processor 48 performs periodic breath tests using the breath alcohol, pressure and temperature signal information received from the sensor head 46. In order to calculate the timing for such tests, and correlate the need for such tests with vehicle operation, the processor may be provided with inputs from the vehicle. A vehicle interface unit 50, providing ignition and transmission status and speed data, is thus also coupled to the processor. Sensors as known in the art may be employed to generate the appropriate signals. A timing/calendar module 52, which may be integral with the microprocessor, provides timing signals for system operation and realtime calendar data for data logging and recordation. The primary output generated by the processor is a control signal to the ignition interlock 56. A control signal freeing the ignition occurs only when a valid initial breath test sample is received, the interlock remaining free so long as the processor indicates that a valid operating condition, as to be discussed subsequently, exists. In case of system failure or other emergency, an override switch 58 may be provided to allow vehicle operation in the absence of breath tests, the operation of the switch being recorded in storage unit 60.

The storage unit also maintains a log of system and vehicle operation, and may be downloaded for analysis. Preferably, the processor is programmed to allow downloading or clearing of storage only upon receipt of a proper password, which typically would not be provided to the vehicle operator, but would be available to law- enforcement personnel, insurance carriers, and the like. This information can include sensed alcohol levels, speed and time of day operating data. The storage unit may also contain the password data, as well as instruction sets for calibration routines, typically accessible only by authorized personnel having a proper access code.

The processor 48 is further adapted to provide an alarm output to the alarm transducers 54 which, in a preferred embodiment, may comprise a relay interface with the lights and/or horn of the vehicle. Other transducers, such as a display on the sensor head case, may also be employed.

To prompt the user for a breath sample, to indicate receipt of a valid sample, and to otherwise indicate system status, one or more displays 56 are provided. Such displays may take any of a variety of visual and/or aural forms. It is intended that at least a portion of the display be located on the sensor head case. In a preferred embodiment, a portion of the display system can be used to provide a readout of the actual alcohol level as sensed by the system. This value may also be stored for retrieval at a later date.

The system may be normally powered by the vehicle battery and electrical system, but with appropriate backup to prevent disabling the system. The backup also insures that the data in storage is not inadvertently lost or destroyed.

In a typical operational cycle as depicted in FIG. 6, the processor receives an input from the vehicle interface unit at 62 indicating that the ignition key has been turned to the "run" position. An initial breath sample is requested on the display 56 at 64. This may be accomplished by appropriate audible and/or visual indicators. The driver then offers an initial breath sample and an initial analysis is performed at 86.

As with each breath test, the processor performs a breath analysis routine 66, first determining if a valid breath sample has been received by consideration of the pressure at 68, temperature at 70 and non-quiescent alcohol sensor output at 72. If each test is passed, indicating a valid sample, a quantitative alcohol level analysis is performed at 74. If the result of any part of the first analysis is a "fail" state, a retest counter is incremented at 76 to allow a retest request to be issued at 80. The test loop is then reentered. If a predetermined number of retests fail to discern a valid breath sample, a fail signal is generated at 82. A fail signal is also immediately generated if the quantitative analysis indicates an excessive alcohol level. If the analysis indicates a proper alcohol level for operation, a pass output is generated at 84.

When the processor is analyzing the initial breath sample, a fail signal causes the ignition to remain in the locked-out mode at 88. A retest can occur only after the passage of a delay interval at 90. With the receipt of a "pass" signal, the engine is allowed to be started at 92, and the "operating" phase of control is entered. Once the vehicle is in gear as monitored at 94, a timing routine provides for a "rolling retest" of breath on a continuing basis at 96. The retest can be based either on a predetermined, fixed schedule, or on a random pattern of time intervals. At the appropriate time, the sample routine 66 in initiated at 98. The receipt of a pass signal allow the timer to be reset at 100 for the next retest. A fail signal causes an alarm state to be entered at 102, such as flashing the vehicle's headlights and brake lights and activating its horn. An alarm state in which the ignition is cut is to be avoided, although it is possible to include a mechanism for shutdown of the ignition after a given period of time to allow the driver to safely stop the vehicle. Such shutdown can be accompanied by a series of warnings to the driver. The alarm state continues until the ignition is shut off, at which time a new initial breath is required to restart the vehicle. In order to insure that breath requests are not unintentionally avoided, a first indicator is activated when a breath sample is required. Should the driver ignore the signal, typically a visual display, a second display, typically oral, is activated after a set period of time, typically 20 seconds. Should the alarms be ignored for an additional period of time, typically 40 seconds, the alarm mode is entered. Once the alarm mode has been activated, it will continue indefinitely until the ignition is shut off. Once the ignition is shut off the system resets, requiring an acceptable breath sample for engine start.

To allow restart of the vehicle in case of a stall without the delay that would be required by an immediate validating breath test, the system monitors the electrical system to sense engine stall or the turning of the ignition key to the off position in the absence of an alarm condition at 104/106. If shutoff occurred as a result of an alarm condition, the routine terminates, the system merely awaiting restart through a new start-up routine. If shutoff has occurred without an alarm condition, a restart timer is activated at 108 and monitoring of engine condition is performed at 112. This allows restart of the engine within a given, preferably short period, without the need for an additional breath test. If restart occurs, the system returns to monitoring gear engagement at 94. If the car is not restarted by timer timeout at 108/110, the engine may be restarted only by commencement of a new starting routine at 62, including the provision of a new initial breath sample.

To prevent the driver from periodically shutting off the engine to take advantage of the "free restart", the rolling retest 96 requires a breath sample within a relatively short period, for example 30 seconds, from the commencement of motion. To prevent the driver from defeating the rolling retest by periodic stopping without engine shutdown, the combination of gear detector 94 and engine condition monitor 104 determine whether the engine is in an idle mode. If an idle is determined, an idle timer is activated at 114. This institutes the breath test routine 66 on a periodic basis during idle periods at 116. As long as the tests are passed, idle can be maintained. Once the idle state is left, as monitored at 118, monitoring of the engine condition at 94 is reestablished. If a breath test is failed during idle, the alarm state is entered at 120, and the ignition must be shut off and a new start routine commenced. The processor cooperates with timing module 52 and storage module 60 to provide data logging to allow the activities of the system to be recorded and stored for an extended period of time. Preferably, the timing/calendar module includes a real time clock calendar data generator while the storage module 60 provides the capacity to hold 60 days of data events at an average rate of at least 500 events per day, or a total of 32,000 events. The processor may preferably also include a communication facility to allow for the bidirectional communication with an external processor for purposes of downloading stored statistics, clearing existing data, and checking and resetting the clock.

In addition to its function in requesting periodic breath samples and validating the samples received, the apparatus may be programmed to provide a continuous sensing of the ambient atmosphere. During such sensing, typically during the intervals where a breath sample is not requested, the temperature and pressure outputs are not processed. In such a mode, the unit can provide an indication of the general atmospheric alcohol level, as may result from the use of alcohol by others besides the driver. Appropriate alarm routines may be provided to indicate improper ambient levels.

Claims

We claim:

1. Apparatus for monitoring a human breath, comprising a first sensor for providing an electrical output signal responsive to the alcohol level of a breath, a second sensor for providing an electrical output responsive to the pressure of the breath, and a third sensor providing an electrical output responsive to the temperature of the breath.

2. The apparatus of claim 1 further comprising a housing for mounting said sensors, said housing having a breath inlet, a breath outlet, and a breath channel therebetween.

3. The apparatus of claim 2 wherein said breath inlet is located at a first end of said housing and said breath outlet is located at an opposed second end of said housing.

4. The apparatus of claim 1 wherein said first sensor is a sensor whose electrical resistance is responsive to the adsorption of ethanol vapors.

5. The apparatus of claim 1 wherein said second sensor comprises a temperature-responsive resistor.

6. The apparatus of claim 6 wherein said second sensor further comprises a second temperature-responsive resistor, said first and second temperature-responsive resistors being arrayed in a bridge configuration, said first temperature-responsive resistor being mounted within said breath channel, said second temperature- responsive resistor being mounted outside said channel.

7. The apparatus of claim 1 wherein said third sensor comprises a radiation generator, a radiation receptor, and means for reflecting radiation from said generator to said receptor proportional to the pressure of a breath flow across said third sensor.

8. The apparatus of claim 7 wherein said reflecting means is a flexible banner.

9. The apparatus of claim 8 wherein said banner is of latex, said radiation generator and receptor are mounted in a head, said banner being affixed to said head.

10. The apparatus of claim 7 wherein said means for reflecting radiation comprises means for generating a series of reflection pulses, the repetition rate of said pulses correlating with the breath flow pressure.

11. The apparatus of claim 10 wherein said pulse generating means comprises a rotatable element having at least one reflective portion.

12. The apparatus of claim 11 wherein said rotating element comprises a body and flow-responsive drive fins mounted thereto.

13. The apparatus of claim 12 wherein said reflective portions are located on said body.

14. The apparatus of claim 12 wherein said at least one reflective portion is located on at least one of said fins.

15. Apparatus for the analysis of breath data in the form of sensor-generated electrical signals, said data comprising alcohol level, breath pressure and temperature components, comprising processing means for comparing each of said components to data representing acceptable values for said components; and means for generating a first output when each of said components are at an acceptable value.

16. The apparatus of claim 15 wherein said processing means includes means for comparing said alcohol level data component to first and second reference values, said first reference value representing ambient conditions and said second reference value representing a maximum acceptable breath alcohol level.

17. The apparatus of claim 15 wherein said processing means includes means for determining the difference between the temperature of the breath sample and ambient temperature and comparing said difference to a minimum acceptable difference value.

18. The apparatus of claim 15 wherein said breath pressure component comprises a pulse train, said processing means including means for determining the repetition rate of pulses of said pulse train and comparing said repetition rate to minimum and maximum acceptable values.

19. The apparatus of claim 15 further comprising means for performing the comparison of said components on a repeating basis.