What term refers to the weight of a gas compared to air?

The term that refers to the weight of a gas compared to air is vapor density. Vapor density is a measure that indicates how heavy or light a gas is in relation to air. It is calculated by taking the molecular weight of the gas and dividing it by the molecular weight of air (approximately 29 g/mol). If the vapor density is greater than 1, the gas is heavier than air and will tend to accumulate in lower areas; if it is less than 1, the gas is lighter and will rise.

Understanding vapor density is crucial for firefighters and emergency responders because it helps them assess the behavior of gases in various environments and allows them to take appropriate safety measures when dealing with hazardous materials or firefighting situations. This concept is especially important when considering the potential for gas accumulation and the risk of asphyxiation or explosion in confined spaces.