Which detection method is based on the presence of smoke?

• A. Fixed temperature
• B. Rate of rise
• C. Smoke
• D. Vapor

Answer: (C)

Smoke-based detection works by sensing smoke particles in the air, using ionization or optical (photoelectric) sensing. It’s designed to respond directly when smoke is present, which is typical of smoldering or early-stage fires. In contrast, fixed-temperature detectors trigger when the surrounding air reaches a preset temperature, and rate-of-rise detectors respond to a rapid increase in temperature. Vapor detectors look for combustion gases or vapors rather than smoke particles. So the method based on the presence of smoke is the one that detects smoke particles in the air.