The physical data term on a Material Safety Data Sheet (MSDS) that indicates if the vapor formed by a material is lighter or heavier than air is called __________.

Correct Answer: Option A — vapor density

Vapor density measures the weight of a vapor compared to an equal volume of air. A value greater than 1.0 indicates the vapor is heavier than air and will accumulate in low-lying areas, creating significant fire and explosion risks in bilges or confined spaces aboard a vessel.