A Flammable Vapor Sensor is a device designed to detect the presence of flammable or combustible gases in the environment. This is a tiny sensor that mounts on a wall, measuring 1.4 by 1.35 by 1.35 inches. In order to prevent gas ignition, the HVAC system is turned off and an alarm is triggered when the concentration of flammable vapors in the air reaches a certain level (50,000 ppm f... https://www.partshnc.com/415-45560-00-bradford-white-flammable-vapor-sensor