What is the SG value listed for Hydrogen Sulphide (H2S)?

What is the SG value listed for Hydrogen Sulphide (H2S)?

• A. 0.97
• B. 1.11
• C. 0.55
• D. 1.19

Answer: (C)

Specific gravity is the density of a gas relative to air. Hydrogen sulfide has a molecular weight of about 34, compared with air’s average around 29, so its SG is about 1.19. That means H2S is heavier than air and will tend to pool in low areas, which is why ventilation, detection, and rescue planning treat it as a gas that can accumulate in depressions or voids. The value 1.19 reflects this heavier-than-air behavior, whereas values below 1 (like 0.55) would indicate a gas lighter than air (such as methane), and values near 1 indicate a gas with density close to air.

Specific gravity is the density of a gas relative to air. Hydrogen sulfide has a molecular weight of about 34, compared with air’s average around 29, so its SG is about 1.19. That means H2S is heavier than air and will tend to pool in low areas, which is why ventilation, detection, and rescue planning treat it as a gas that can accumulate in depressions or voids. The value 1.19 reflects this heavier-than-air behavior, whereas values below 1 (like 0.55) would indicate a gas lighter than air (such as methane), and values near 1 indicate a gas with density close to air.