Which of the following statement is true concerning the meter shown in the illustration? See Illustration SF-0003

Correct Answer: Option A — As gas samples are drawn into the instrument they are burned within the case.

Catalytic combustion-type explosimeters draw flammable gas samples across a heated filament inside a balanced Wheatstone bridge circuit. The combustible gases burn on the filament surface, changing its resistance and indicating hydrocarbon vapor concentrations relative to the lower explosive limit.