Agent concentration is defined as which?

• A. The portion of agent in air expressed in volume percent
• B. The total mass of agent in space
• C. The time to detect agent
• D. The chemical composition of agent

Answer: (A)

Concentration is the portion of the clean agent in the air, expressed as a volume percent. In clean-agent design, we describe how much agent is present by comparing the volume of agent vapor to the total air volume and writing that as a percentage by volume. This is a ratio of volumes, which is the standard way to describe gas mixtures in a space. The other ideas don’t define concentration: the total mass of agent in space is a mass measure and doesn’t reflect how much of the air is actually agent at a given moment; the time to detect agent relates to detection speed, not how much is present; and the chemical composition describes what the agent is made of, not how much of it is in the space.