asd meaning in oil and gas

A device used in conjunction with a gas pilot flame in a variety of LPG heaters, it is also referred to as an Oxyanalyser. If oxygen in the vicinity is depleted due to combustion of the gas and lack of sufficient ventilation to replace the oxygen, the pilot flame becomes unstable and lifts away from the mouth of the pilot jet ~ thereby allowing the thermocouple probe to cool down and causing an electro-magnetic (solenoid) gas valve to slam shut, cutting off the gas supply and preventing further oxygen depletion.