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

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

Combustible gas indicators operate by drawing a sample into a chamber where it is oxidized over a heated platinum filament. The resulting temperature rise, proportional to the gas concentration, is measured by a Wheatstone bridge circuit. This catalytic combustion process provides an accurate reading of the atmosphere's flammability.