Chemical CO Detector for an Automatic Gas Safety Shutoff Valve. Final Report, June 1984-September 1988

摘要

A low cost sensor for carbon monoxide has been developed that exhibits a reversible color change when exposed to CO. Based on a proprietary mixture of metal salts, the solid state sensor gradually changes color from pale yellow to a blue which intensifies with continued exposure to CO in a way that parallels the buildup of carboxyhemoglobin levels in the blood. Technical performance goals were achieved for the CO sensor in laboratory feasibility studies. The chemioptical sensor was integrated into an automatic, photooptic shutoff control system for use with vented and unvented space heaters. The shutoff control was self-powered, using photovoltaic panels to convert light from the space heater pilot light into the electric energy required for operation of electronics. Light from the pilot was directed through a fiber optic cable to the CO sensor, behind which was a photooptic detector. Darkening of the sensor by CO reduced the detector output until a relay, holding the fuel valve open, was deenergized. No nuisance failures were reported among ten space heaters, modified with CO safety shutoffs and placed in residential sites during 10/87 for the 1987-88 heating season. In 5/88 each site was revisited. The shutoff valves on all operational units performed properly when exposed to a controlled level of CO.