Abstract: An apparatus for determining the proportion of gases in a gas mixture, has a measurement chamber having a chamber defining structure, a gas inlet and a gas outlet, an ultrasound source and an ultrasound detector mounted such that the ultrasound source is capable of transmitting ultrasound through the chamber to the ultrasound detector; a temperature sensor mounted such that the sensor is capable of sensing the temperature in the chamber. The chamber defining structure is adapted to amplify thermal exchange with a gas content in the chamber so as to suppress a temperature change in the chamber.

Abstract: A docking station for use with gas sensors includes limited test and diagnostic circuitry directed to specific characteristics of selected detectors. Where a family of detectors is to be evaluated, a universal interface for that family can be included. A single port can be used for multiple different detectors irrespective of specific detector characteristics.

Abstract: A method is provided for indicating the useful service life of a gas filtration and purification system comprising steps of embedding two or more mass-responsive electronic sensors (e.g., surface acoustic wave devices) in a sorbent bed of a filtration cartridge, wherein the mass-responsive electronic sensors are coated with a non-conductive absorptive organic polymer; passing a gas containing a volatile chemical of interest through the filtration cartridge and in contact with the two mass-responsive electronic sensors; and measuring a difference in an electronic property between the two mass-responsive electronic sensors. In such a manner, the two mass-responsive electronic sensors act as internal references with respect to each other, thereby eliminating variations in temperature, interferents, pressure, and the like.

Abstract: A reaction chamber enables a reaction between received elemental mercury gas and an oxidizing agent gas. The reaction chamber includes a porous (or permeable) medium through which to pass the elemental mercury gas and the oxidizing agent gas. Passing of the elemental mercury gas and the oxidizing agent gas through the porous medium supports a number of useful functions. For example, the porous medium enhances mixing of the elemental mercury gas with the oxidizing agent gas to enhance a reaction. Also, the porous medium increases an amount of surface area in a reaction chamber on which reactions (e.g., heterogeneous surface reactions) can take place between the elemental mercury gas and the oxidizing agent gas to form oxidized mercury gas. Accordingly, the reaction chamber configured to include a porous medium enhances a conversion of elemental mercury gas into oxidized mercury gas.

Abstract: In the calibration of a lambda sensor (26), inaccuracies occur during a fuel cut-off overrun phase depending on the temperature. A method is proposed for correcting an output signal of a lambda sensor (16) of an internal combustion engine (1), having the following steps: detection of a fuel cut-off overrun phase of the internal combustion engine (1), sensing of an exhaust-gas composition by the lambda sensor (16) during the fuel cut-off overrun phase, sensing of a temperature which represents a measure of the intake air of the internal combustion engine (1), calibration of the lambda sensor (16) based on the second temperature.

Abstract: A method for calibrating a flex fuel sensing apparatus having a fuel passage involves the use of a generally solid test blank having a size and shape configured to match that of the fuel passage. The test blank comprises material having a known, predetermined dielectric constant. The test blank is inserted into the fuel passage where the dielectric constant of the test blank is operative to simulate the presence of various gasoline and ethanol fuel blends. The test blank may also comprise a deformable/compressible solid such as rubber where the test blank is compressed during calibration to eliminate air gaps or the like, improving accuracy. The use of the solid test blank reduces complexity compared to using actual gasoline/ethanol blends for calibration as well as reduces post-calibration cleanup.

Abstract: The invention concerns a sensor with silicon-containing components from whose sensitive detection element electrical signals relevant to a present analyte can be read out by means of a silicon semiconductor system. The invention is characterized in that the silicon-containing components are covered with a layer made of hydrophobic material in order to prevent unwanted signals caused by moisture.

Abstract: A method of calibrating a gas sensor that generates an output related to the concentration of a sensed gas, the method comprising: i) obtaining the value of said output or a related value at each of a set of known values of a first variable and at each of a set of known values of a second variable, one of the variables being gas concentration; ii) for each value of said second variable, determining a first best fit function relating said output or related value to the first variable, each best fit function utilizing at least one coefficient whose value is determined; iii) for the, or the corresponding, coefficient values from each of the first best fit functions, determining a second best fit function relating said coefficient to the second variable, and replacing the coefficient values in the first best fit functions by the second best fit function, and, iv) repeating step iii) for each further coefficient, if any, in the first best fit functions so as to generate a final function relating said output or

Abstract: A calibration card and method of manufacturing and using the card to calibrate an analytical instrument capable of reading a photoluminescent oxygen probe. The card includes at least (a) a first mass of a first solid state composition comprising an oxygen-sensitive photoluminescent dye that is the same as the probe dye, embedded within an oxygen-permeable carrier matrix that is the same as the probe carrier matrix, wherein the first composition has a first sensitivity to oxygen, and, (b) a second mass of a second solid state composition comprising an oxygen-sensitive photoluminescent dye that is the same as the dye in the first mass, embedded within a carrier matrix that is different from the carrier matrix in the first mass, wherein the second composition has a known second sensitivity to oxygen that is less than the first sensitivity to oxygen.

Abstract: An apparatus (7) for monitoring particles flowing in a stack (6), comprises: an electrical-interaction monitor (1) operable to provide a signal (300) resulting from electrical interaction of the particles with the monitor (1). a scattered-light monitor (10) operable to provide a signal (310) resulting from detection of light scattered from the particles, and a controller (320) arranged to alter the calibration of the electrical-interaction monitor 1 in response to changes in the relative magnitude of the electrical-interaction (signal 300) and the scattered-light signal (310).

Abstract: A compact gas sensor array, to which a test gas can be admitted without the use of mechanical components and whose readiness for measurement is interrupted during the calibration only briefly. The array includes a combination of an electrochemical gas sensor (3) and an electrochemical gas generator (2). A gas channel (1) is provided from the gas generator (2) to the measuring electrode (9) of the gas sensor (3). The measuring gas from the environment of the gas sensor (3) has free access to the measuring electrode (9).

Abstract: Tracer gas leak detection is provided by a calibration system with a gas leak detector having a test port for receiving a sample containing a tracer gas and coupled to a vacuum pump; a calibrated leak for a calibration sample containing the tracer gas; a mass filter coupled to the test port for receiving the test sample in an operating mode, coupled to the calibrated leak through a calibrated leak valve for receiving the calibration sample in a calibration mode, having controllable transmission of the tracer gas and providing a filtered sample; detector detecting the tracer gas in the filtered sample; a programmable gain element providing a measured value of leak rate in response to the detector signal; and a controller configured, in response to a mode control signal, to operate the leak detector in the calibration mode over two or more working ranges using the calibrated leak.

Abstract: Several methods of calibrating a wavelength-modulation spectroscopy apparatus configured to measure a concentration of an analyte in a sample gas are disclosed. Each of the methods allows for calibration and recalibration using a relatively safe gas regardless of whether the sample gas for which the concentration of the analyte can be determined is a hazardous gas. In one embodiment of the invention, calibration that is sample-gas specific is accomplished by determining a first slope coefficient and calibration function for the sample gas, after which a scaling factor can be determined based on the first slope coefficient and a second slope coefficient for the same or a different sample gas and used in a subsequent calibration (or recalibration) to scale the calibration function. In other embodiments of the invention, calibration that is not sample-gas specific is accomplished to allow for the determination of the analyte concentration in variable gas compositions and constant gas compositions.

Abstract: The invention relates to a method for measuring the permeability to gases of the wall of a hollow body (6) made of polymeric material, characterized: in that it comprises a first conditioning step during which a flushing gas flushes said hollow body (6), and a second measuring step during which a measurement gas is introduced into said hollow body (6); in that the flow of flushing gas is greater than the flow of the measurement gas, and; the flushing gas is sent into the hollow body (6) without mixing with the measurement gas.

Abstract: One disclosed feature of the embodiments is a control processor in a vapor delivery system for chemical vapor deposition precursors. A pressurization rate processor calculates first and second pressurization rate curves at first and second time instants. A volume calculator computes consumed volume based on first and second volumes at the respective first and second time instants. The first and second volumes are computed using slopes of lines fitting the first and second pressurization rate curves.

Abstract: An inspection device inspects a humidity sensor having a sensor portion and a circuit portion, which are integrated into one chip. The inspection device includes: an inspection chamber for accommodating a wafer, in which a plurality of humidity sensors are disposed as a sensor chip in a wafer state; a probe for contacting an electrode pad of the circuit portion; a tester electrically connected to the probe for inspecting electric properties of the humidity sensor; and a temperature-humidity control portion for controlling a temperature and a humidity in the inspection chamber.

Abstract: System and method are utilized for testing the performance of a gas monitor against predetermined monitor characteristics to determine if performance of a gas monitor is validated following testing gas being directly delivered to a gas sensor of the gas monitor.

Abstract: A system for testing and calibrating gas sensors with gas stored in a strip of packets. The strip may be fed into a chamber having a defined volume of air. A packet may be punctured with a mechanism to release one or more gases into the volume of air to result in an air-gas mixture. New air may be moved into the chamber to push the mixture out of the chamber to a sensor for testing and/or calibration. Then another packet may be punctured to release one or more gases into the volume of new air in the chamber for another air-gas mixture. This mixture may be moved out of the chamber, in the same manner as the previous mixture, to another sensor for testing and/or calibration. This procedure may be repeated with additional packets on the strip.

Abstract: The invention relates to a device for measuring the ammonia content in a gas mixture. The device comprises at least one inlet and one outlet for the gas mixture, between which is situated an ammonia measuring system connected thereto. The device also comprises first regulating means for regulating the gas mixture flow through the inlet, and second means which are adapted such that they allow a measurement of the ammonia content which is substantially independent of the gas mixture flow rate. The device is preferably applied for measuring the ammonia content in exhaled air.

Abstract: An apparatus for use in a sample monitoring system is provided and includes a first enclosure configured to enclose a probe body into which the sample is drawn, a sensor coupled to the probe body and configured to sense a chemical composition of the sample and at least one first heater configured to heat an interior of the first enclosure, a second enclosure configured to enclose a pump coupled to the probe body and configured to draw the sample therein and a second heater configured to heat the pump, and a third enclosure configured to enclose a pump motor configured to control an operation of the pump and to support heating controlling units configured to control the at least one first heater and the second heater.

Abstract: A dissolved oxygen measurement system, and a method for calibrating a dissolved oxygen analyzer are provided. The method includes directing a pressurized cleaning fluid, having a known oxygen content, upon a sensing surface of a dissolved oxygen sensor disposed in a fluid. Then, the analyzer waits until the dissolved oxygen sensor response to the pressurized cleaning fluid is relatively stable, and stores a calibration value relative to the dissolved oxygen sensor response to the pressurized cleaning fluid. A dissolved oxygen measurement system is also provided. The system includes a dissolved oxygen sensor disposed in a fluid and a first source of a first compressed cleaning fluid that has a first dissolved oxygen content. A dissolved oxygen analyzer is coupled to the dissolved oxygen sensor and to the first valve and is configured to obtain a first calibration value related to the first dissolved oxygen content.

Abstract: A portable, calibratible gas detector includes a multi-position gas inflow limiting orifice. When this orifice is in a calibrating position, a source of calibrating gas can be activated to provide a quantity of gas that diffuses into ambient atmosphere flowing through the orifice. The calibration gas can then be sensed.

Abstract: Methods and devices for detecting photoresist coating failures are disclosed. A disclosed method to detect a photoresist coating failure on a semiconductor wafer comprises: loading a photoresist coated wafer on a notch position check block; rotating the coated wafer; detecting the position of a notch in the wafer; blowing air toward the surface of the wafer with at least one air nozzle located over the rotating wafer; detecting an amount of the air blown from the at least one air nozzle; and generating a coating failure signal if a variation in the amount of air blown from the at least one air nozzle is indicative of a photoresist coating failure.

Abstract: Usually, a sniffing leak detector must be calibrated for each tracing gas. The calibration comprises ranging of the spectral positions into the mass spectrum and the amplitude height. At least one mass line is determined with a calibrating gas. The mass lines lying between two mass lines and/or between a zero point and a line are determined by interpolation and/or extrapolation. In this manner, a sniffing leak detector can be used for such tracing gases which have not previously been used for calibration purposes.

Abstract: A device for calibration of a humidity sensor with a measuring chamber includes a first gas connector for connection to a pressurizing unit and a second gas connection for connection to a further gas chamber. The first and/or the second gas connector may have a flow resistance which may be adjusted to two different fixed values.

Abstract: A gas sensor diagnostic method (or apparatus) is arranged to periodically obtain sensor output values of a gas sensor such as an oxygen sensor for an internal combustion engine, and to determine local extreme values from the sensor output values obtained during a period of interruption of fuel supply to the engine. Moreover, the local extreme values are compared with a first predetermined threshold level. When the number of the local extreme values reaches a predetermined first number, a diagnosis is performed to determine whether the gas sensor is in an improper condition or not, in accordance with results of the comparison of the local extreme values with the first threshold level.

Abstract: Apparatus for testing a hazard detector, the apparatus comprising electrically-powered generating means arranged to generate at least two stimuli for application to the detector; and control means arranged to control the generation of each stimulus by said stimulus generating means, wherein said generating means includes a carbon monoxide generator.

Abstract: A method of confirming reception of a drop of water has the steps of applying a powder on a surface of a gas sensing element, placing the element in a gas passage so as to expose the surface of the element to the gas passage, causing a measured gas to flow through the gas passage, receiving drops of water included in the measured gas on limited areas of the surface of the element such that the drops of water take out the powder applied on the limited areas from the element, and confirming the reception of the drops of water on the surface of the element. The powder has a melting point or a sublimation temperature equal to or higher than 1000° C.

Abstract: A method of measuring the gas flow of an incondensable gas in a flowing mixture of said incondensable gas and a condensable gas comprising the steps of calibrating a leak detector; injecting a known quantity of gauge gas at a known mass flow rate into said flowing mixture of gases; drawing a sample of the said gauge mix off at a sample point; passing said sample through a condenser so as to remove said condensable gas from the gauge mix, resulting in a test mix; passing the said test mix into the leak detector so as to measure the concentration of the gauge gas within the test mix; and calculating the mass flow rate of said incondensable gas within said flowing mixture. There is also provided a method of measuring the rate of ingress of an incondensable gas at an ingress point along a flow path of a flowing mixture of said incondensable gas and a condensable gas.

Abstract: A system for calibrating a response to an exhaust-stream NOx level in a motor vehicle is provided. The system comprises a NOx sensor that includes an electrode, a current from the electrode responsive to the exhaust-stream NOx level while a bias voltage is applied to the electrode. The system further comprises a controller configured to interrupt the bias voltage and to adjust a motor-vehicle response to the current based at least partly on an attained voltage of the electrode while the bias voltage is interrupted. Other embodiments provide a method of calibrating a NOx sensor response in terms of gain and offset parameters.

Abstract: In a change from a lean to a rich exhaust gas mixture, a characteristic behavior appeal's in a short time interval in the vicinity of the lambda jump of an upstream catalytic converter lambda probe in the signal characteristic which is measured by a downstream catalytic converter lambda probe. From the signals in small intervals, around the instant of changing, the reliability performance of the downstream lambda probe can be deduced without the actual probe jump in curves of the voltage characteristics having to be considered.

Abstract: A particulate sampler system includes a diluted exhaust mass flow controller that receives flow from a dilution mass flow controller and a laminar flow element (LFE). The dilution mass flow controller and LFE are fluidly arranged parallel to one another. A controller communicates with the mass flow controllers and the LFE to determine the flow through these devices, command valves in the mass flow controllers and generate data for determining calibration coefficients and correction factors. The diluted exhaust mass flow controller is calibrated and calibration coefficients are generated using a first to fourth order curve fit. Similarly, initial calibration coefficients are generated for the dilution mass flow controller. The diluted exhaust mass flow controller is set at a desired flow point. The dilution mass flow controller is varied between set points corresponding to different dilution ratios at the common, desired set point.

Abstract: An electrochemical gas sensor testing device that includes a test signal generator that generates a multiplexed signal that includes a first test signal that includes alternating current (AC) and is free from a direct current (DC) component and a second signal that includes a DC bias voltage, an electrochemical cell that includes a counter electrode, a sensing electrode, and an electrolyte, the counter electrode and the sensing electrode being in electrical communication with the electrolyte and each other, the counter electrode being in electrical communication with the signal generator to receive the multiplexed signal generated by the signal generator, and a processor that receives an AC signal from the sensing electrode and that analyzes the AC signal.

Abstract: Embodiments of the invention provide novel, industrially applicable, and non-obvious apparatus and methods for automatically, routinely, and accurately calibrating a trace detection portal. Embodiments of the apparatus include a calibrant container; a substance (or substances) uniquely identifiable by a trace detection portal as a calibrant; unique placement of the calibrant container's outlet relative to a substance collection port of a sample collection chamber; and/or computer executable instructions that, when executed by a computer processor, cause a consistent release of a measured amount of calibrant into the sample collection chamber upon command and/or at pre-determined time intervals.

Abstract: A method for operating a sensor for recording particles in an exhaust gas flow and a device for carrying out the method are provided, in which at least one measure of the exhaust gas flow is ascertained and in which the measure of the exhaust gas flow is taken into consideration in the valuation of the particle sensor signal made available by the particle sensor. The procedure is based on the knowledge that the exhaust gas flow, for instance, the exhaust gas volume flow, has an influence on the particle sensor signal made available by the particle sensor, especially when the measuring effect is based on the depositing of particles on a sensor surface. Using the procedure, a possibly present cross sensitivity of the particle sensor with respect to different exhaust gas flows is taken into consideration, so that the measuring accuracy is increased.

Abstract: A procedure for the calibration of the lambda measuring signal supplied by the wideband lambda sensor, which is disposed in the exhaust gas area of an internal combustion engine, and a device to implement the procedure are proposed. During the procedure, a correction value is used to ascertain a unit of measurement for the lambda actual value, whereby the correction value is ascertained during a specified operating state of the internal combustion engine, in which no fuel metering occurs and the engine rotational speed of the internal combustion engine lies above a threshold value. The correction value—is ascertained as a function of the sensor temperature of the wideband lambda sensor during a specified operating state.

Abstract: An oxygen analyzer system includes first and second internally calibrated sensors each for detecting oxygen levels, and a processing subsystem responsive to the sensors. The processor is configured to calibrate the first sensor while the second sensor detects oxygen levels, and to calibrate the second sensor while the first sensor detects oxygen levels. The processor is further configured to compare the oxygen level detected by the first internally calibrated oxygen sensor and the oxygen level detected by the second internally calibrated oxygen sensor, to output an error signal if the oxygen levels detected by the first internally calibrated sensor differ from the oxygen level detected by the second internally calibrated oxygen sensor by a predetermined amount, and to output the oxygen level detected by either the first or second internally calibrated oxygen sensor if the oxygen levels detected thereby do not differ by a predetermined amount.

Abstract: A portable detector is described for monitoring a gas in an atmosphere. The detector comprises a housing, at least one gas sensor carried by the housing, and electrical connectors carried by the housing for establishing electrical connections to a calibration apparatus and a microprocessor carried by the housing. The microprocessor controls the calibration apparatus via signals provided to microprocessor through the connectors to initiate the supply of calibration gas to the detector at a predetermined rate.

Abstract: The invention concerns a procedure to determine a mass of particles or a particle mass flow in an exhaust gas system of an internal combustion engine, whereby at least one resistive particle sensor is disposed in the exhaust gas system of the internal combustion engine. The measured signal change of the particle sensor is compared with a predicted signal change of the particle sensor ascertained from an engine model. If the measured signal change of the particle sensor and/or the predicted signal change of the particle sensor are corrected while taking into account the influencing variables on the transverse sensitivities of the particle sensor, it is possible when ascertaining the predicted signal change of the particle sensor that a compensation for the transverse sensibilities can result even during dynamic operating point changes of the internal combustion engine, which occur faster than the actuation of the particle sensor.

Abstract: A portable, relatively low power gas detector incorporates a single pellistor-type sensor for sensing an explosive gas of interest. Outputs from the sensor are corrected in accordance with ambient temperature and humidity and pre-stored correction factors based on characteristics exhibited by a plurality of similar sensors.

Abstract: A gas amount measuring device including a vacuum container, a first pipe, an air release valve being attached to the first pipe, a second pipe, a calibration gas generator being attached to the first pipe, a third pipe, a vacuum gauge, a first valve, a leak valve, a second valve, a turbomolecular pump, a third valve, and a roughing pump being attached to the third pipe in order from a vacuum container side, a first bypass pipe connecting the third pipe between the vacuum container and the first valve to the third pipe between the leak valve and the second valve, a fourth valve being attached to the first bypass pipe, and a second bypass pipe connecting the third pipe between the leak valve and the second valve to the third pipe between the third valve and the roughing pump, a fifth valve being attached to the second bypass pipe.

Abstract: A method is described to determine the remaining sorption capacity of activated-carbon-sorbent gas filters by measuring the breakthrough time for a test gas challenge to a test filter with known and controlled test conditions that include flow rate and temperature and the use of a calibration curve that has been established by prior testing of the test filter sorbent medium in calibration tests where the filter is exposed to a known quantity of gas surrogate for the challenge gases that the filter may sorb in service and then testing the test filter medium by challenge with a sparged gas that can be selectively detected to determine the breakthrough as a function of test gas. The apparatus using such a method comprises a portable system that includes a sparging test gas generator, a carrier gas system, a test filter canister holder, and a selective detector that can quantitatively monitor the test gas exiting the test filter canister.

Abstract: A calibration arrangement for breathalyzers wherein a heightened degree of control and management is applied. Broadly contemplated are arrangements whereby jars or containers of new solution to be used in the calibration arrangement are subject to automatic verification. Also contemplated is the close monitoring of the running of calibration tests and safeguards to ensure that extensively used or old solution is not put into use.

Abstract: The present invention relates to the monitoring of gas concentrations possible in very low ranges (i.e., low ppb and even ppt ranges) and especially use thereof in environmental monitoring, exposure assessment, bomb detection, and health studies. The invention can use a spatial and temporal assessment of gas concentrations that enables the sources of the gas in question to be located and identified which is useful in environmental and health field but can also be applied to other fields an example of which is detecting and locating explosives. This technology can uses small, light weight, and low power components that allow for the monitor to be portable and even worn on a person as a personal monitor. This technology can be used in a stationary monitors as well.

Abstract: The present invention relates to the monitoring of gas concentrations possible in very low ranges (i.e., low ppb and even ppt ranges) and especially use thereof in environmental monitoring, exposure assessment, bomb detection, and health studies. The invention can use a spatial and temporal assessment of gas concentrations that enables the sources of the gas in question to be located and identified which is useful in environmental and health field but can also be applied to other fields an example of which is detecting and locating explosives. This technology can uses small, light weight, and low power components that allow for the monitor to be portable and even worn on a person as a personal monitor. This technology can be used in a stationary monitors as well.

Abstract: Articles of manufacture and methods of making and using same concern a container having an internal space and a passivated internal metal surface. The container contains a composition of an acid gas and a balance gas contained within the internal space and in contact with the passivated internal metal surface. The stability of the acid gas concentration over time is enhanced.

Abstract: A testing module for use with a gas detector, includes a plurality of gas inlets and outlets, each outlet being in fluid connection with one of the inlets. Each of the outlets is adapted to mate with and form a fluid connection with one of the inlets of a second like testing module. Gases can then flow from the outlets of the testing module into the inlets of the second like testing module. A gas container module for use with a gas container, includes a plurality of gas inlets and outlets, each inlet being in fluid connection with one of the outlets. Each of the inlets is adapted to mate with and form a fluid connection with one of a the outlets on a second like gas container module. Gases can then flow from the outlets of the second like gas container module into the inlets of the gas container module.

Abstract: A particulate matter (PM) sensor includes an embedded self-calibrator. The PM sensor is to be installed in an exhaust corridor of an internal combustion engine. The PM sensor can self-calibrate by imposing a known potential across a protective housing in which the conductive probe is suspended. An image charge that is imposed upon the conductive probe is fed back and correlated to generate an updated calibration for the PM sensor.

Abstract: A system and methodology for the trace detection of organic explosives is described. The detector system combines a separation system, such as a gas chromatograph to separate the components of an explosive mixture, with a pyrolysis detector. In operation, effluent from the separation system is pyrolyzed and the fragments produced on pyrolysis of the explosive compound are then detected. The small molecule fragments exhibit sharply banded, characteristic spectrum, enabling detection of the explosive materials. The system is tested using the explosive materials nitrobenzene and 2,4-dinitrotoluene, and with the nitramine explosive tetryl. Detection limits are 25 ng for nitrobenzene, and 50 ng for 2,4-dinitrotoluene. Tetryl is detected with a detection limit of 50 ng.

Abstract: A sensor supervision system for periodically providing a test to accesses the status of a gas detection sensor, such as a carbon monoxide (CO) sensor, is provided. To access the status of the CO sensor, a processor provides a voltage to the sensor supervision system, such that a voltage is applied to CO sensor, charging the CO sensor. The status of the CO sensor is accessed by determining the change in the voltage charge of the CO sensor between two sampling time points. If the first sample voltage is substantially equal to the second sample voltage, i.e., a substantially constant voltage, the carbon monoxide sensor fails the test. However, if there is an change is the voltage change between the first and second sampled time points, the CO sensor passes the test.