Blaze Through the 2025 Firefighter FACT Exam – Ignite Your Path to Bravery!

Vapor density is the mass of a certain volume of a substance compared to the mass of an equal volume of air. The lower the vapor density, the lighter the vapor of that substance will be compared to air. Ethanol has the lowest vapor density among the options provided.

Ethanol is lighter than air, which means its vapor will rise quickly and dissipate in the atmosphere. This characteristic is important for safety considerations in firefighting and handling chemicals, as it affects how quickly a substance can evaporate and potentially create flammable vapors.

In contrast, gasoline, acetone, and kerosene have higher vapor densities compared to ethanol, meaning their vapors will be heavier and may accumulate in low-lying areas, posing greater risks of fire and explosion. Understanding the properties of these liquids, including vapor density, is crucial for firefighters to ensure safe handling and effective response to incidents involving these substances.