NGA 70 Properties Of Natural Gas And Abnormal Operating Conditions Practice Test

The concept here is how to read the specific gravity of a gas relative to air, which tells you whether the gas will tend to rise or sink in air. Specific gravity for gases is basically a comparison of densities, and in practice it’s closely tied to the gas’s molar mass. Carbon monoxide has a molar mass of about 28 g/mol, while air is around 29 g/mol. That makes the SG of CO roughly 28/29, which is about 0.97, commonly cited as near 0.97–0.98. So the option around 0.98 best represents carbon monoxide’s SG: it is lighter than air (SG less than 1), so leaks will tend to rise and disperse upward rather than pool on the floor. The other numbers imply the gas is much lighter or heavier than air (0.88 would be even lighter than CO but still not the standard value; 1.10 and 1.20 would mean the gas is heavier than air), which does not match CO’s known properties. Using 0.98 aligns with the standard data and practical understanding of CO behavior in ventilation and leak scenarios.