The specific gravity standard for gases is?

The specific gravity standard for gases is based on air. This means that the specific gravity of a gas is defined as the ratio of the density of that gas to the density of air under the same conditions of temperature and pressure. By using air as a reference point, you can determine how heavy or light a gas is compared to air. A specific gravity of less than one indicates that the gas is lighter than air and will rise, while a specific gravity of greater than one indicates that the gas is heavier than air and will tend to sink. This standardization is essential for various applications, such as in gas detection and ventilation design, as it informs operators and engineers about the behavior of gases in different environments.

Water and hydrogen are not used as the standard for gases in this context because their densities do not provide a relevant or practical baseline for comparing the vast array of gases encountered in wastewater treatment and other fields.