Explosimeter

An explosimeter is a gas detection instrument used to measure the amount of combustible gas present in the air, most often preset for methane, hydrogen or carbon monoxide, with correlation factors applied to read other gases. It works by heating a wire and exposing it to a sample of the surrounding air; combustible gas burning at the hot wire raises its electrical resistance, which a Wheatstone bridge circuit converts into a reading, and the instrument includes a flashback arrestor to keep the flame from escaping into the surrounding atmosphere. Explosimeters warn workers when gas concentration approaches a set percentage of the lower explosive limit, sounding an alarm before ignition sources, even ordinary sparks from battery powered equipment, can trigger an explosion in an environment where flammable gas has accumulated.