Abstract: A water heater includes a gas valve and a solenoid to operate the gas valve. A thermocouple of the water heater is heated by a pilot light to provide a current source to maintain the gas valve in an open position. A sensor activated switch switches current from a second current source to the solenoid to move the gas valve to a closed position.

Abstract: A sensor and method for rapidly determining the absence of a vapor in a gas or fluid is described as well as a method for constructing the sensor. The sensor comprises a resistive element having first and second leads; an elastomeric material in thermal contact with and surrounding a portion of the resistive element; and a stratum of electrically conductive particles surrounding a portion of the elastomeric material and electrically coupled to the first lead and a third lead. The method for determining the absence of a vapor comprises linking the sensor to a control means for preventing excessive adsorption; exposing the sensor to an environment; and monitoring the sensor.

Abstract: A valve stem gas leak sensor or detector configured to surround a possibly leaking petrochemical or like flow line valve stem and provide for external monitoring equipment an electrical resistance related to the amount of hydrocarbon gas leakage occurring around the valve stem. Such a gas leak detector, termable a ring sensor, is configured as a stem surrounding enclosure, with interconnecting segments for ease of installation around and removability from a valve stem, with one or both of each such segments having an interiorly arranged layer of gas sensor particulate material characterized by change in electrical resistance in the presence of a changing concentration of hydrocarbon gas leakage around a valve stem, and with interengaging connector/conductor pins holding the segments together around the valve stem and across which the electrical resistance of one or both gas sensor material layers can be measured with the ring sensor in place on the valve stem.

Abstract: Combination hydrocarbon and water level sensor systems for use in connection with underground storage sites, such as gasoline storage tanks, industrial waste sites, and the like, with a solar cell power source and an LCD display located above ground and providing directly viewable indication of the presence or absence in the underground environment of "HYDROCARBON" and/or "WATER", with the absence of such being indicated by "OK". In the preferred form, a pod containing an adsorptive type hydrocarbon gas sensor and a galvanic cell type liquid water sensor is suspended by electrical cable means from a well cap in which the solar cell and LCD display are installed.

Abstract: A thermo-electrically regulated adsorptive sensing device comprising a gas adsorptive sensing element having a stratum of adsorbently sensitive particles, a thermistor for sensing the temperature of the sensing element, a thermo-electric module for controlled cooling and heating of the sensing element, a heat sink, and a controller unit for applying variable amounts of electrical current through the thermo-electric module to appropriately heat or cool the sensing element in a rapid, controlled and accurate fashion. The thermo-electric module may be operated either to maintain the stratum of particles of the sensing element within about 1.degree. (0.6.degree. C.) of the optimal sensing temperature or operated to heat the particles in a controlled fashion to a relatively high purging temperature at which the gas is relatively rapidly desorbed, and then cool the particles in a controlled fashion to a relatively lower sensing temperature at which the gas is relatively rapidly adsorbed by the particles.