What does it mean when a gas has a vapor density less than 1?

When a gas has a vapor density less than 1, it means that the gas is lighter than air. In this case, it will rise when released into the atmosphere because, in general, lighter gases tend to ascend while heavier gases will settle. This behavior is a result of buoyancy, which dictates that substances with lower density will float or rise in a medium with a higher density, such as air.

Understanding vapor density is crucial in various applications, especially in firefighting and hazardous materials management, as it informs responders about how a gas will behave in different environments. For example, knowing that a particular gas will rise can help in planning ventilation strategies and mitigation measures during an incident involving gas leaks.