In the field the first part of the system is the sensor that picks up the target gas, in a Petrochemical environment this is typically flammable gas. With Zone 1 or 2 rating which requires the deployment of ATEX or IS equipment at the gas source. Zone One is defined as an area where an explosion is likely to take place, perhaps because of maintenance work or commissioning. Zone Two is defined as an area where an explosion is unlikely to take place only in the event of an accident or unusual operational circumstances
To see if a gas detector works a “Bump Test” is performed. Jargon buster –this means applying the correct gas for the sensor, to check the sensor responds by viewing the reading on the instrument display real time. Typically within 10% accuracy.