Which detector projects a beam of light across a large open area?

Which detector projects a beam of light across a large open area?

• A. A beam detector monitors carbon monoxide levels.
• B. A beam detector uses a photodiode to detect heat.
• C. Projects a narrow beam of light across a large open area from a sending unit to a receiving unit. When the beam is interrupted by smoke it activates the alarm.
• D. A beam detector stores fire extinguishers.

Answer: (C)

Beam detectors project a narrow beam of light across a large open area from a sending unit to a receiving unit, and the alarm is triggered when smoke interrupts that beam. This setup is ideal for big spaces where multiple spot detectors aren’t practical because it relies on a continuous optical path that smoke can break, signaling a fire condition. The other options describe different devices or functions—gas detectors for carbon monoxide, a sensor type that isn’t how a beam system detects smoke, and an unrelated use for extinguishers—so they don’t fit the described mechanism.

Beam detectors project a narrow beam of light across a large open area from a sending unit to a receiving unit, and the alarm is triggered when smoke interrupts that beam. This setup is ideal for big spaces where multiple spot detectors aren’t practical because it relies on a continuous optical path that smoke can break, signaling a fire condition. The other options describe different devices or functions—gas detectors for carbon monoxide, a sensor type that isn’t how a beam system detects smoke, and an unrelated use for extinguishers—so they don’t fit the described mechanism.