To mitigate the risk of fire in your new data center, you plan to implement a heat-activated fire detector. Your
requirement is to have the earliest warning possible of a fire outbreak. Which type of sensor would you select
and where would you place it?

A.
Rate-of-rise temperature sensor installed on the side wall

B.
Variable heat sensor installed above the suspended ceiling

C.
Fixed-temperature sensor installed in the air vent

D.
Rate-of-rise temperature sensor installed below the raised floors

Explanation:
Heat-activated detectors provide the earliest warning possible of a fire outbreak. They should be placed below
the raised floors as this is where the cabling most likely to cause an electrical fire is.
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. The sensors can either be spaced uniformly throughout a
facility, or implemented in a line type of installation, which is operated by a heat-sensitive cable.
It is not enough to have these fire and smoke detectors installed in a facility; they must be installed in the right
places. Detectors should be installed both on and above suspended ceilings and raised floors, because
companies run many types of wires in both places that could start an electrical fire. No one would know about
the fire until it broke through the floor or dropped ceiling if detectors were not placed in these areas.
Incorrect Answers:
A: A side wall is not the best location for the sensor. If cabling under a raised floor starts a fire, it will be some
time before the wall mounted heat sensor is triggered. Therefore, this answer is incorrect.
B: A variable heat sensor is not the best type of sensor to provide the earliest warning possible of a fire
outbreak. Therefore, this answer is incorrect.C: Fixed-temperature sensors are triggered when a defined temperature is reached. This is not the best type of
sensor to provide the earliest warning possible of a fire outbreak. The air vent is also not the best location for
the sensor. Therefore, this answer is incorrect.

Harris, Shon, All In One CISSP Exam Guide, 6th Edition, McGraw-Hill, 2013, p. 470