Gas-free engineer
A gas-free engineer is a person who has successfully completed a similarly named training course offered by the United States Navy. The gas-free engineer is thereby qualified to certify a confined space as being safe to enter without the use of an air-purifying or supplied air respirator. The confined space would, however, need to be ventilated during entry to ensure an adequate supply of breathable air.
Gas Free Engineering is equivalent to Firefighter team lead, Toxic Gas inspector, Confined space inspector, etc.
