How is specific gravity defined in terms of gas?

Specific gravity in the context of gases is defined as the weight of the gas compared to the weight of an equal volume of air at the same temperature and pressure. This means that when measuring specific gravity, we assess how heavy the gas is relative to air, which serves as a baseline for comparison.

When we compare gases, it's essential to understand that air is less dense than many gases like carbon dioxide and propane. Thus, gases with a specific gravity greater than 1 are heavier than air and will tend to rise when released. Conversely, gases with a specific gravity of less than 1 are lighter than air and will rise. This property is crucial in applications such as ventilation, as it helps determine how gases disperse in the atmosphere.

Understanding the specific gravity of a gas relative to air enables welders and other professionals to work safely, keeping in mind the behavior of different gases in various environments.