Abstract: A plate-type NO.sub.x gas sensor having a WO.sub.3 sensing film which are capable of preventing temperature variation of a sensing thin film depending on gas flow to decrease heat loss thereof, whereby extending the life span of batteries of a portable gas sensor. The plate-type NO.sub.x gas sensor includes a Pt thin film electrode formed on a front surface of an alumina substrate, a tungsten oxide thin film for sensing NO.sub.x gas deposited on the front surface of the substrate on which the Pt thin film electrode is formed, a heater formed on a back surface of the alumina substrate for holding a portion of the tungsten oxide thin film for sensing NO.sub.x gas within a predetermined temperature range, a conducting wire for connecting between the Pt thin film electrode and the heater and a sheet made of at least one material selected from a group composed of Al.sub.2 O.sub.

Abstract: A sensor for selectively detecting HC classes, e.g., alkanes, alkenes and aromatics, in a gas mixture comprising a metal oxide seiniconductor catalyst which is catalytically active for the selective HC classes; the reactions selected from the group consisting of partial oxidation, oxidative dehydrogenation, oxidative coupling and isomerization. Each of these reactions results in imparting a change in the electrical conductivity of the metal oxide which is proportional to the concentration of the HC in the gas mixture. Suitable metal oxide catalysts include Bi.sub.2 O.sub.3 --MoO.sub.3, CoO--MoO.sub.3, SnO.sub.2 --MoO.sub.3, TeO.sub.2 --MoO.sub.3, Sb.sub.2 O.sub.5 --V.sub.2 O.sub.5 --MoO.sub.3, SnO.sub.2 --Sb.sub.2 O.sub.5, Nb.sub.2 O--V.sub.2 O.sub.5 --MoO.sub.3, V.sub.2 O.sub.5 --MoO.sub.3, ZnO--Fe.sub.2 O.sub.3, Li.sub.2 O--MgO, V.sub.2 O.sub.5 --P.sub.2 O.sub.5, metal oxide compounds of a spinel or perovskite crystalline structure, and mixtures thereof.

Abstract: The present invention provides a gas sensor element having physical, electrical and chemical properties capable of detecting methane and carbon monoxide selectively with 1 intergrated filtering, catalyzing sensor by improving gas selectivity of the semiconductor gas sensor. The present invention relates to a gas sensor element, which has a carbon monoxide sensor layer with an ability to function as a catalyst film that blocks carbon monoxide, which impedes detection of methane, and has a layer-built structure where the surface of a methane sensor is covered with the carbon monoxide gas sensor which can be obtained by a gas-phase method.

Abstract: An air fuel ratio sensor having an externally located heat source and an optical fiber heat introduction member. The heat introduction member is inserted into an inside chamber of a sensor element having a U-shaped cross section, and is connected to the external heat source outside the sensor element for introducing heat from the external heat source into the inside chamber. The heat introduction member is further connected to a temperature detector outside the sensor body. Accordingly, an air fuel ratio sensor can have sufficient durability and sufficient starting performance, and a temperature inside the sensor element can be readily detected.

Abstract: The present invention provides a device for measuring air quality. The device includes at least one sensor with a sensor resistance which is converted via signal processing into an output signal, the gas sensing or air content sensing device having its sensor(s) with electrical resistance that is a function of the air quality, such sensors being connected in an astable flipflop circuit arrangement with a first feedback resistor, a second feedback resistor, a capacitor and a comparator--where the first resistor is coupled between the inverting input and output of the comparator, and the second resistor is coupled between the noninverted input and the output of the comparator, and the sensor(s) is/are coupled between a reference potential and the noninverting input of the comparator. The output signal has a period which is related to the sensor resistance.

Abstract: The selectivity of response of resistive gas sensors to specific gases or vapors is improved by the selection of specified gas-sensitive materials which are not previously known for the applications described, which include detection of hydrocarbons in the presence of CO, H.sub.2 S, SO.sub.2, chlorine, NO.sub.2, CO.sub.2 (especially in low concentrations), CFC's, ammonia, free oxygen by determination of partial pressures, and numerous organic gases and vapors.

Abstract: Chemically sensitive sensors, suitable for detecting analytes in fluids (in gaseous or liquid phase), characterised in that the chemically sensitive sensors comprise a chemically sensitive probe, which comprises one or a blend of several arylene alkenylene oligomers.

Abstract: A gas sensor determines the presence of at least one designated gas in a gaseous environment. The gas sensor comprises a semiconductor substrate; a thin insulator layer disposed on the semiconductor substrate; a catalytic metallic gate disposed on the thin insulator layer; and a chemically modified layer disposed on the catalytic metal gate. The chemically modified layer comprises a material that protects the sensor from corrosive gases and interference from at least one foreign matter and water, alters at least one of surface chemical properties and surface physical properties of the sensor, and passes only the designated gas therethrough.

Abstract: A kit for monitoring mammalian reproductive cycles by monitoring variations in the quantity of one or more low molecular weight volatile compound having a molecular weight of less than 50 grams per mole present in a body constituent sample is disclosed. Samples of a body constituent selected from the group consisting essentially of humoral fluid, breath and body cavity air are collected from a female mammal a multiple number of times during the reproductive cycle. The quantity of a low molecular weight volatile compound in each sample is measured. In the preferred embodiment, the low molecular weight volatile compound, acetaldehyde, will be measured and monitored. Variations in the quantity of the low molecular weight volatile compound appearing in each sample is monitored to determine the phase of the mammal's reproductive cycle and to predict the occurrence of ovulation.

Abstract: In a biosensor system for detecting trace compounds resulting from a fire or from plants damaged by destructive insects, a live chemoreceptor is provided for sensing the trace compounds, and a semiconductor component is connected to the chemoreceptor for providing sensor signals when the chemoreceptor senses the presence of trace compounds.

Abstract: A gas sensor and method for manufacturing a gas sensor is provided. In order to increase the selectivity and the sensitivity to a gas to be measured, a gas-sensitive gallium oxide layer of a gas sensor is coated with a filter layer that comprises silicon dioxide. In an alternative embodiment, the gallium oxide layer can be coated with a gas-sensitive metal oxide layer made of titanium oxide, aluminum vanadate, tungsten oxide or tantalum oxide.

Abstract: The present invention and its claims encompass principles, methods, apparatus, and applications for detection, quantification, and monitoring of responses of gases, vapors, aerosols, and mixtures thereof to initiators of exothermic reactions. While the invention can be utilized for any concentration level, the intended, normal utilization is for gases in which the concentrations of species capable of participating in exothermic chemistry are too low to support self-sustaining exothermic reactions leading to detonations or deflagrations as well as for gases in which other factors prevent the exothermic reaction chemistry from becoming self-sustaining. This abstract shall not be construed to define or limit in any way the scope of the invention, which is measured by the appended claims.

Abstract: Oxygen sensor for measuring resistance as a function of oxygen partial pressure, made of alkaline-earth-doped perovskitic lanthanum ferrites with the general formulaLa.sub.1-x Me.sub.x FeO.sub.3-.delta.where Me is one of alkaline earth metals, Mg, Ca, Sr, and Ba, x is a degree of doping of the lanthanum ferrites. The oxygen sensor oxygen deficit of anion is 6=0 to 0.25, and the degree of doping of the lanthanum ferrites is x=0.1 to 0.3 and is selected to provide a temperature independent resistance property to the oxygen sensor in a lean range.

Abstract: An NO.sub.x sensor is produced by sintering a plurality of columnar crystals of .beta.-type Nb.sub.2 O.sub.5. The average value M of aspect ratios b/a (wherein a represents a width and b represents a length) in the columnar crystals is set in a range of 2.11<M.ltoreq.5. The NO.sub.x sensor has a high sensitivity to NO.sub.x via an enhancement attained by control of crystal type and structure.

Abstract: The invention provides a gas sensor for selective detection of hydrocarbons in low-oxygen gases, having a capacitive element and a gas-permeable sensitive layer as a dielectric. The sensitive layer is a precious-metal-doped zeolite which has a regular crystalline structure made of primary pores whose diameter is in the order of the gas-kinetic diameter of the gas molecules to be detected.

Abstract: Chemical sensors for detecting analytes in fluids comprise first and second conductive elements (e.g. electrical leads) electrically coupled to and separated by a chemically sensitive resistor which provides an electrical path between the conductive elements. The resistor comprises a plurality of alternating nonconductive regions (comprising a nonconductive organic polymer) and conductive regions (comprising a conductive material) transverse to the electrical path. The resistor provides a difference in resistance between the conductive elements when contacted with a fluid comprising a chemical analyte at a first concentration, than when contacted with a fluid comprising the chemical analyte at a second different concentration. Arrays of such sensors are constructed with at least two sensors having different chemically sensitive resistors providing dissimilar such differences in resistance.

Abstract: The invention pertains to a solid-state chemical sensor with a substrate support. On one side of the support is mounted a heating element with branch circuit connections. On the other side interdigital electrodes are arranged and thereon a carbon dioxide-sensitive material, which comprises CuO and TiO.sub.3, as well as additional metal oxides, in the form of a thick film of approximately 20-200 .mu.m.

Abstract: A polymeric gas sensor utilizes a variety of electrode geometries to generate varied responses to selective gases. The characteristic response to various gases of each electrode geometry permits the construction of a gas sensor having desirable and reproducible characteristic responses to specific gases. The gas sensor array of the invention produces characteristic responses from a plurality of sensors. These responses collectively produce a characteristic response pattern that can be used for the identification of specific gases with pattern recognition techniques.

Abstract: The invention is a sensing method and an oxygen sensor for detecting a change of oxygen partial pressure in an ambient atmosphere through a change of a measurable physical property of a sensing material. The sensor includes a sensing material selected from metal or its oxides which, when at an elevated temperature and exposed to a gas containing a changing partial pressures of oxygen, is capable of changing from one metal or metal oxide phase to another such oxide phase and vice versa. Associated with such phase change is a change in a measurable physical property of the material. The sensor also includes heating means, connectable to a power source, maintaining a temperature gradient across the sensing material since it is critical that the sensing material exist in at least two phases during active sensing. An output signal is furnished in response to the change in a physical property, like electrical resistance, of a portion of or of the entire material in response to change in oxygen partial pressure.

Abstract: A sensor for detecting combustible gases in a test gas. The core of this sensor is comprised of a sensitive layer based on a semiconducting metal oxide that is deposited on a ceramic substrate and for which the electrical resistance provides information on the concentration of combustible gases in a test gas. The sensitive layer (3) is comprised of a compound (12) of sintered-together grains (15) of the semiconducting metal oxide, the surface of which is coated with gold and/or a gold alloy. The semiconducting metal oxide in this case is stannic oxide (SnO.sub.2), indium oxide (In.sub.2 O.sub.3), titanium oxide (TiO.sub.2) or another n-semiconducting metal oxide or metal mix oxide. The gold alloy, for example, is composed of 66 mol % gold and 33 mol % palladium (Pd).

Abstract: A chemical switch device comprising a film which irreversibly reacts upon exposure to specific chemical components in the environment under the conditions of measurement. The reactions can lead to large changes in the physical and chemical properties of the film which are measurable electrically, optically or by other methods.

Abstract: Provided is an odour sensor which may be useful for discriminating between the odour of human or other mammalian individuals, and perimidine monomers and polymers which may be used in such a sensor.

Abstract: An improved area monitor for detecting gas concentration is provided that requires a very infrequent calibration, and works reliably in detecting a particular target gas using only two semiconductor sensors. One of these sensors will exhibit a drift that is constantly monitored and automatically compensated for, while the other sensor exhibits a stable, repeatable response over very long periods of time. Once the "stable" has been initially calibrated, the concentration of the target gas can be discerned directly from the resistance of this sensor, although more that one particular chemical gas may cause the stable sensor to change resistance. The second sensor is then used to discern whether or not the change in resistance of the stable sensor was due to the actual target chemical, or due to some other similar chemical. The second sensor is selected to be of a type that responds in one direction (i.e.

Abstract: A thermal gas sensing apparatus for a gas detector is provided with a gas compartment containing a gas, a gas sensor exposed to the gas in the gas compartment, and a temperature sensor exposed to the gas in the gas compartment. The gas sensing apparatus includes a circuit for generating a gas signal having a magnitude which relates to the heat capacity of the gas and a circuit for generating a temperature signal having a magnitude which relates to the temperature of the gas. The apparatus includes a circuit for supplying a variable magnitude of electrical current through the gas sensor to cause the resistance of the gas sensor to remain substantially constant. The apparatus also includes a difference amplifier for generating a gas concentration signal based upon the temperature signal and the gas signal.

Abstract: A chemical switch device comprising a film which irreversibly reacts upon exposure to specific chemical components in the environment under the conditions of measurement. The reactions can lead to large changes in the physical and chemical properties of the film which are measurable electrically, optically or by other methods.

Abstract: A thin film hydrogen sensor, includes: a substantially flat ceramic substrate with first and second planar sides and a first substrate end opposite a second substrate end; a thin film temperature responsive resistor on the first planar side of the substrate proximate to the first substrate end; a thin film hydrogen responsive metal resistor on the first planar side of the substrate proximate to the fist substrate end and proximate to the temperature responsive resistor; and a heater on the second planar side of the substrate proximate to the first end.

Abstract: The invention is a sensing method and an oxygen sensor for detecting a change of oxygen partial pressure in an ambient atmosphere through a change of a measurable physical property of a sensing material. The sensor includes a sensing material selected from metal or its oxides which, when at an elevated temperature and exposed to a gas containing a changing partial pressures of oxygen, is capable of changing from one metal or metal oxide phase to another such oxide phase and vice versa. Associated with such phase change is a change in a measurable physical property of the material. The sensor also includes an electrical heating source, connectable to a power source, maintaining a temperature gradient across the sensing material since it is critical that the sensing material exist in at least two phases during active sensing.

Abstract: In a technique for detecting organic vapors and aerosols, e.g. of amines, hydrazines and nitrogen-containing compounds produced in combustion, molecules condense at a surface of a conductive device. By heating the conductive device in pulsed fashion, e.g. by resistance heating, condensed molecules are thermally ionized and emitted from the conductive device. Emitted ions are collected by a collector electrode, and the resulting ionic current pulse is amplified by a transimpedance circuit. The heat pulse lasts until the ionic current pulse has subsided, by which time the conductive device has become free of residual substances. As a result, the conductive device remains uncontaminated and has a long service life. The time-averaged power consumption of the technique is less than 2 mW. For resistance heating, a meander heater element can be disposed on a silicon nitride membrane across an etched opening in a silicon chip.

Abstract: Acid/base measuring sensor systems consisting of arrays of basic sensor cells are described which are constructed based on the chemical/electrical response characteristics of poly(aromatic amines). Protonation (doping) or deprotonation (de-doping) of the --N.dbd.sites in the polymers leads to characteristic conductivity vs. concentration curves which can be calibrated to produce reliable, instantaneous readings of the acid/base concentrations at various points in the working environment.

Abstract: A nitrogen oxide detecting sensor, according to the present invention, incorporates a gas detecting portion including, as a main component thereof, an oxide compound having electric conductivity or semiconductivity, the oxide compound having a crystal structure of 2212 phase and expressed generally as: Bi.sub.2 Sr.sub.2 (Ca.sub.1-x Y.sub.x)Cu.sub.2 O.sub.8.+-..delta. where 0.6.ltoreq.x<1; 0.ltoreq..delta..ltoreq.1. Electrodes are electrically connected to the gas detecting portion. When the gas detecting portion is analyzed by X-ray diffraction using cuK.alpha. rays to obtain diffraction peak values thereof in the range of a diffraction angle between 5.degree. and 65.degree., the diffraction peak values having a sum .SIGMA. I?2212! expressed by one of the following:(a) .SIGMA. I?2212!/.SIGMA. I?T!>88.1%(b) {.SIGMA. I?2212!+.SIGMA. I?2201!}/.SIGMA. I?T!>94.8%(c) {.SIGMA. I?2212!+.SIGMA. I?Y.sub.2 O.sub.3 !} .SIGMA. I?T!>88.1%(d) {.SIGMA. I?2212!+.SIGMA. I?(Bi, Ca) O!}/.SIGMA. I?T! >88.8%where .

Abstract: A continuous emission monitoring system is disclosed for detecting toxic substances of various types in either stack gas or ambient air. Particular systems are illustrated for monitoring lewisite and chromium(VI). Each system employs a gas sampler that utilizes a high-volume, wet cyclone concentrator unit which scrubs the contaminants from the gas into water or another suitable scrubbing solution. In-line chemical processing of the contaminated sample thus obtained is accomplished either within the sampling unit or by an external chemistry processing module. After processing to provide an analyte in the sample indicative of the presence of a predetermined contaminant, the sample stream is delivered to an ion chromatograph or other analyzer to determine the presence and quantity of the analyte and indicate whether a danger level has been reached. This provides monitoring on an essentially real-time or near real-time basis.

Abstract: A method for determining the presence of a first gas in a second gas uses a gas sensor made up of at least two pairs of electrodes, each pair of electrodes having different spacing between the electrodes. The electrodes of the gas sensor have surfaces that are reactive to the gases under investigation. The gas sensor is exposed to the gases, and the electrical resistances between the pairs of electrodes are measured over a period of time. `The results are compared with a calibration curve to determine if the first gas is present in the second, and to determine of the sensor is malfunctioning.

Abstract: A method for forming a solid state humidity sensor is disclosed which comprises the steps of: (a) dissolving a tungstate salt into an aqueous solution; (b) adjusting the pH of the aqueous tungstate salt solution to below 8.5; (c) forming one or a pair of electrodes on an insulating substrate; (d) placing the substrate into the pH-adjusted aqueous tungstate salt solution and heating the aqueous solution containing the substrate at temperatures above 70.degree. C. to thereby form a pyrochlore-type crystalline tungsten trioxide film over the electrode or pair of electrodes; and (e) forming another electrode over the pyrochlore-type crystalline tungsten trioxide film if only one electrode is formed during step (c).

Abstract: A photoionization detector includes a brittle substrate having a void micromachined therein with a void inlet and a void outlet. First and second electrodes are disposed in the void. An ultraviolet transparent member covers at least a portion of the void in which the electrodes are disposed. A gas sample passes through the void and is exposed to ultraviolet radiation from a UV source. Ionization of the sample is measured as current flowing between the electrodes.

Abstract: In order to avoid measurement signal drift, a gas sensor has a gas sensitive layer which is provided on its upper side with a measuring electrode structure and on its lower side with an electrically conductive layer.

Abstract: A sensor device of the present invention is capable of surely detecting occurrence of a fire and a type of the fire. The sensor device includes a detection element made of an organic semiconductor element or an inorganic semiconductor element which is varied in characteristic value (i.e., resistance) thereof by both gas produced in a flaming-type fire and a smouldering-type fire and of which a variation in resistance by gas produced in a flaming-type fire is different in polarity from that by gas produced in a smouldering-type fire. A resistance of the detection element is extracted by a resistance extractor and then fed to a resistance decrease discriminator and a resistance increase discriminator, wherein a decrease or increase in resistance of the element is discriminated. An information output circuit outputs a predetermined signal depending on discrimination results provided by the discriminators, to thereby detect occurrence of a fire and/or a type of the fire.

Abstract: A self-contained, integrated-structure, miniature, electrochemical-type oxygen sensor is described which uses an oxygen ion conducting solid electrolyte. An encapsulated metal-metal oxide reference electrode on one surface of the solid electrolyte provides a reference oxygen pressure. A sensing electrode is placed on the other surface. The voltage developed between the reference electrode and the sensing electrode is indicative of the oxygen content of the fluid the sensing electrode is contacting.

Abstract: The capacitance type gaseous sensing device (10) includes a first electrode layer (12) formed on a semiconductor substrate layer (14). A seed layer (16) is formed on the first electrode layer (12). A reorganized layer (18) is formed on the first electrode layer (12) through interaction with the seed layer (16) to form a porous sensing layer. A second electrode layer (20) is formed on the reorganized layer (18). The reorganized layer (18) absorbs gaseous elements that change the dielectric constant of the capacitance type sensor device (10). A change in the dielectric constant causes a change in the capacitance of the reorganized layer (18) as measured across the first electrode layer (12) and the second electrode layer (20).

Abstract: A gas sensor including a substrate, a heater formed on said substrate, and a gas sensing material to be heated by said heater, wherein the area of the substrate under the heater is removed or reduced in its thickness to form a cavity. The thickness of the layer of the gas sensing material is reduced gradually toward the peripheral of the gas sensing material.

Abstract: A resistive gas sensor has a porous semiconducting oxide body in which the pore surfaces are decorated with a precious metal. The sensor operates at ambient temperatures for detection and measurement of target gases, especially carbon monoxide. The porous sensor body is formed of primary crystallites agglomerated together, the agglomerate size being less than 10 times the primary crystallite size, and the primary crystallite size having an average diameter of less than 5 micrometer. From 0.05 to 80% of the pore surfaces are covered by the metallic phase, the metallic phase consisting of particles having an average size of less than 50 nanometers. Presence of the target gas is indicated by a change in electrical resistance of the sensor.

Abstract: A resistive gas sensor having a WO.sub.3 sensing element is especially useful for detection of low concentrations (1 ppm or less) of ozone in air. The WO.sub.3 element is a porous layer with a 30-60% porosity and less than 50 micrometer thick, having in general a sufficiently open porous microstructure and high surface area to give satisfactory response to ozone. The sensor is used for detection of low ozone concentrations at a working temperature in the range from ambient to 600.degree. C.

Abstract: Apparatus and methods for the measurement of total organic carbon, total inorganic carbon, total carbon and total heteroorganic carbon of deionized water are described. In a preferred embodiment, the sample is split into a first stream and a second stream. Inorganic carbon in the first stream is measured using a temperature and conductivity cell, and then the organic carbon in the first stream is oxidized in a U.V. oxidation module. The resulting carbon dioxide is transferred through a carbon dioxide permeable membrane into the second stream. The second stream then passes into a second temperature and conductivity cell for the measurement of total carbon.

Abstract: A multilayered ceramic integrated sensor 200 for monitoring auto exhaust gases is capable of existing in the relatively harsh environments of the exhaust stream of an internal combustion engine. The integrated sensor 200 may include discrete devices such as an oxygen sensor 104, a hydrogen sensor 206, an NO.sub.x sensor 208, and a carbon monoxide sensor 210. The device 200 may further include a temperature sensor 202 as well as total combustion calorimetric sensor 102. The multilayered ceramic integrated sensor may be fabricated from a plurality of layers of ceramic material disposed in stacked relationship with respect to one another.

Abstract: In a gas sensor for sensing reducing or oxidizing gases which comprises a semiconductive metal oxide film, there are provided stripe-like outer electrodes which define therebetween a continuous surface area and stripe-like inner electrodes which extend between, and parallel to, the outer electrodes so as to divide the continuous surface area into longitudinal segments which have different properties with respect to reducing or oxidizing gases such that different conductivity changes are generated for the different segments upon exposure to oxidizing or reducing gases.

Abstract: The invention is a sensing method and an oxygen sensor for detecting a change of oxygen partial pressure in an ambient atmosphere. The sensor includes a sensing material selected from metal or its oxides which, when at an elevated temperature and exposed to a gas containing a changing partial pressures of oxygen, is capable of changing from one metal or metal oxide phase to another such oxide phase and vice versa. Associated with such phase change is a change in a measurable physical property of the material. Heating elements, connectable to a power source, able to maintain a temperature gradient across said sensing material are necessary to maintain the material, during active sensing operation, in at least two of the phases defining a boundary line therebetween which is generally perpendicular to the longitudinal axis of the temperature gradient.

Abstract: A gas sensor for detecting the presence of gases in air. In particular, sensors are described that have a compound catalytic support structure and are suitable for sensing hydrocarbons and nitrogen oxides. The device features a ceramic substrate having a temperature sensitive resistor on one surface. A mixture of ceramic particles and glass powder are applied over the substrate and resistor and fired so that the glass flows and adheres the ceramic particles to the substrate. A catalyst layer of either platinum or rhodium is deposited on the catalyst support and a thermally sensitive resistor element detects reactions of hydrocarbons or nitrogen oxides on the corresponding catalyst. The invention is suitable for sensing gases in the harsh environment of an automobile exhaust system.

Abstract: A gas sensor for detecting the presence of a specified gas within a mixture includes a silicon substrate, a silicon nitride membrane supported by the substrate, a thin gold sensor trace deposited on the membrane, and a thin gold reference trace deposited on the membrane. A molybdenum adhesion layer is employed between the membrane and the gold traces. The electrical resistance of the sensor trace changes when the sensor trace adsorbs molecules of the gas. Solid state construction facilitates quick and efficient regeneration of the sensing capability of the gas sensor. The silicon nitride membrane and the molybdenum adhesion layer do not adversely affect the resistivity of the gold traces. An alternate gas sensor embodiment includes an integrally formed heater element.

Abstract: A novel, inexpensive sensor and method for detecting volatile compounds in the gas phase at concentrations of less than about 500 ppm in ambient air are provided. The sensor comprises (a) a dielectric substrate having a major surface; (b) a pair of electrically conductive electrodes disposed on the major surface of the substrate; and (c) a conductive polymer covering the pair of electrically conductive electrodes, with the conductive polymer doped with appropriate dopants in measurable excess of that stoichiometrically required to change the conductive polymer from a neutral state to a charged state to provide requisite conductivity. A method for making the sensor is provided, as is a method of use of the sensor which relates to its use in a monitoring system comprising a means for measuring the conductivity of the sensor connected to a warning means for providing an indication when the conductivity reaches a predetermined level.

Abstract: A gas sensor has a gas sensing component which permits measurement of a change in optical absorption and, optionally also a change in electrical conductivity on exposure to an environment containing certain gases. The gas sensing component comprises a metal bis aromatic macrocycle which may be a new mixed rare earth metal bis tetrabenzoporphyrin or tetrabenzoazaporphyrin.

Abstract: A gas sensor has at least a measuring electrode and a counter electrode on an electrolyte layer. This gas sensor is improved with respect to the complete extent of the electrochemical reaction achieved of the gas molecules, which are to be detected, at the measuring electrode by the manner of determining an electrical charge developed or accumulated thereat. To solve this task, the invention provides that the measuring electrode (14) has component electrodes (14a, 14b) which enclose the electrolyte layer (11, 12) in the manner of a sandwich.