Question 97Safety & Environmental - 1st Asst/Chief

The correct answer is A) vapor density. Vapor density is the physical data term on a Material Safety Data Sheet (MSDS) that indicates whether the vapor formed by a material is lighter or heavier than air. Vapor density is a measure of the weight of the vapor compared to the weight of an equal volume of air. If the vapor density is less than 1, the vapor is lighter than air and will rise. If the vapor density is greater than 1, the vapor is heavier than air and will sink. The other options are incorrect because they do not directly indicate whether the vapor is lighter or heavier than air. Vapor pressure measures the tendency of a material to evaporate, vapor gravity is not a commonly used term, and vapor level does not specify the relative weight of the vapor.