Which type of gravity compares the weight of a gas to an equal amount of air?

Specific gravity is a measure that compares the weight of a substance, in this case, a gas, to the weight of an equal volume of air. This concept is essential in gas certification as it helps determine how a gas will behave in the atmosphere, whether it will rise or fall when released. When the specific gravity of a gas is less than that of air, it means that the gas is lighter than air and will tend to rise. Conversely, if the specific gravity is greater than that of air, the gas is heavier and will tend to sink. Understanding specific gravity is crucial for safety and proper handling of gases in various applications, such as in leaks or ventilation systems.

Other terms, while related to weight and buoyancy, do not specifically measure a gas against air in the same context. Relative gravity generally refers to the weight of an object compared to another object in a more general sense and lacks the specific context of air and gases. Absolute gravity and apparent gravity address different gravitational concepts that do not pertain directly to gas comparisons with air.