For hydrogen sulfide detection, sensitized tapes indicate the presence of this gas by means of discoloration of an exposed spot on the tape. The shade of the color on the spot depends upon the concentration of the gas and __________.

Correct Answer: Option D — duration of exposure

Sensitized tape detectors for hydrogen sulfide rely on a chemical reaction that produces a color change. The intensity of this discoloration is cumulative, meaning it depends not only on the concentration of the gas present but also on the total duration of exposure to the sampling medium during the test.