Several different types of smoke and fire detectors can be used. What type of detector is shown in the following graphic?

A.
Photoelectric

B.
Heat-activated

C.
Infrared flame

D.
Ionization

Explanation:
A: A photoelectric device, also referred to as an optical detector, detects the variation in light intensity. The detector produces a beam of light across a protected
area, and if the beam is obstructed, the alarm sounds. If the light source is obscured, the alarm will sound.
B is incorrect because heat-activated detectors can be configured to sound an alarm either when a predefined temperature (fixed temperature) is reached or
when the temperature increases over a period of time (rate-of-rise). Rate-of-rise temperature sensors usually provide a quicker warning than fixed-temperature
sensors because they are more sensitive, but they can also cause more false alarms.
C is incorrect because an infrared flame detector reacts to emissions of flames and senses pulsation of flames. This type of detector does not use a beam of
light to identify smoke; thus, it is not a smoke detector. This type is a fire detector because it actually initiates when it is affected by flames.
D is incorrect because an ionization detector reacts to charged particles of smoke. It is a smoke detector and not a fire detector because it activates when it
encounters smoke particles. It does not use a beam of light to identify smoke, but has sensors that can identify the charged (ionized) components within the smoke
itself.