Certified Fire Investigator Practice Exam

What is defined as the gas phase of a substance, especially for those typically liquids or solids?

1. Aerosol

2. Vapor

3. Fume

4. Gas

The correct answer is: Vapor

The term that is defined as the gas phase of a substance, particularly when that substance is usually found as a liquid or solid at room temperature, is vapor. Vapor specifically refers to the gaseous state of a substance that can readily transition back to its liquid or solid form under certain conditions, such as changes in temperature or pressure. This concept is significant in fire investigation, as it relates to how various materials can create flammable vapors that may lead to combustion when mixed with an appropriate concentration of air. Understanding vapor is crucial for recognizing how fires can start and spreading. While gas is a broader term encompassing all gaseous substances, vapor specifically highlights those substances that are normally not in gaseous form under standard conditions, which is why this answer is particularly relevant in the context of the question regarding liquids and solids.