Certified Fire Investigator Practice Exam

What is the vapor density of methane?

1. 1.00

2. .55

3. .75

4. 1.20

The correct answer is: .55

Vapor density is the weight of a certain volume of gas compared to the weight of the same volume of air under the same conditions. For methane, the vapor density is approximately 0.55. This means that methane is lighter than air, as a vapor density of less than 1 indicates that the substance will rise when released into the atmosphere. Understanding vapor density is crucial in fire investigation, particularly when assessing potential fire hazards or when determining how gases may behave during a fire incident. Since methane is a common flammable gas, knowing its vapor density helps in evaluating the risks associated with its accumulation in enclosed spaces.