Which detector is a line-of-sight device?

Which detector is a line-of-sight device?

• A. Flame detector
• B. Rate-of-rise heat detector
• C. Water temperature switch
• D. Video smoke detector

Answer: (A)

Line-of-sight sensing requires an unobstructed path between the detector and the fire so the detector can pick up the flame’s radiant energy. A flame detector is built to sense the specific ultraviolet or infrared radiation emitted by flames, so it must be able to “see” the flame to trigger. That dependence on a direct view is what makes it the line-of-sight option among these choices. The other devices detect fire in different ways: rate-of-rise detectors respond to a rapid increase in temperature rather than flame radiation and don’t rely on visibility to the flame; water temperature switches monitor temperature in a water line and aren’t fire detectors; video smoke detectors rely on image analysis of smoke patterns, not on detecting flame radiation itself, so they’re not the line-of-sight flame detector in this context.

Line-of-sight sensing requires an unobstructed path between the detector and the fire so the detector can pick up the flame’s radiant energy. A flame detector is built to sense the specific ultraviolet or infrared radiation emitted by flames, so it must be able to “see” the flame to trigger. That dependence on a direct view is what makes it the line-of-sight option among these choices. The other devices detect fire in different ways: rate-of-rise detectors respond to a rapid increase in temperature rather than flame radiation and don’t rely on visibility to the flame; water temperature switches monitor temperature in a water line and aren’t fire detectors; video smoke detectors rely on image analysis of smoke patterns, not on detecting flame radiation itself, so they’re not the line-of-sight flame detector in this context.