APPENDIX C

Properties of H2S

Hydrogen sulfide is colorless, transparent, and flammable, smells like "rotten eggs" at very low concentrations, and is denser than air and thus may accumulate in low places.

The slightest presence of H2S in the air is normally detectable by its characteristic "rotten-egg" odor; however, it is dangerous to rely on odor as a means of detecting life-threatening concentrations because the sense of smell is lost rapidly, allowing lethal concentrations to accumulate without warning.

Table AT1 describes the poisonous nature of hydrogen sulfide.

Table AT1. Effects of hydrogen sulfide.
Concentration of H2S
Effect
(%)
(ppm)
(g/100 ft3)
0.001 10 0.65 Obvious and unpleasant odor; safe for 8 hr
0.002 20 1.3 Safe for 4 hr exposure
0.01 100 6.48 Kills sense of smell in 3–15 min; may sting eyes and throat
0.02 200 12.96 Kills sense of smell; stings eyes and throat
0.05 500 32.96 Dizziness; breathing ceases in minutes; need prompt artificial respiration
0.07 700 45.26 Unconscious quickly; death will result if not rescued promptly
0.1 1000 64.8 Unconscious immediately, followed by death within minutes

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