Combustible gas indicators operate by drawing an air sample into the instrument __________.
Official USCG Answer & Rule Citation
Correct Answer: Option C — over an electrically heated platinum filament
Combustible gas indicators operate on the Wheatstone bridge principle, drawing air samples across an electrically heated platinum filament. Combustible vapors burn catalytically on the filament, increasing its electrical resistance and proportionally deflecting the meter needle.
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