2 cissp ® Official Study Guide Eighth Edition

Class
Type
Suppression material
A
Common combustibles
Water, soda acid (a dry powder or liquid chemical)
B
Liquids
CO2, halon*, soda acid
C
Electrical
CO2, halon*
D
Metal
Dry powder
* Halon or an EPA-approved halon substitute 
Water cannot be used on Class B fires because it splashes the burning liq-
uids and such liquids usually float on water. Water cannot be used on Class 
C fires because of the potential for electrocution. Oxygen suppression 
cannot be used on metal fires because burning metal produces its own 
oxygen.

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Chapter 10 
■
Physical Security Requirements
Fire Detection Systems
To properly protect a facility from fire requires installing an automated detection and 
suppression system. There are many types of fire detection systems. 
Fixed-temperature 
detection
systems trigger suppression when a specific temperature is reached. The trigger 
is usually a metal or plastic component that is in the sprinkler head and melts at a specific 
temperature. There is also a version with a small glass vial containing chemicals that vapor-
ize to overpressurize the container at a specific temperature. 
Rate-of-rise detection
systems 
trigger suppression when the speed at which the temperature changes reaches a specific 
level. 
Flame-actuated
systems trigger suppression based on the infrared energy of flames. 
Smoke-actuated
systems use photoelectric or radioactive ionization sensors as triggers. 
Incipient smoke detection systems, also known as aspirating sensors, are able to detect the 
chemicals typically associated with the very early stages of combustion before a fire is oth-
erwise detectible via other means.
Most fire-detection systems can be linked to fire response service notification mecha-
nisms. When suppression is triggered, such linked systems will contact the local fire 
response team and request aid using an automated message or alarm.
To be effective, fire detectors need to be placed strategically. Don’t forget to place them 
inside dropped ceilings and raised floors, in server rooms, in private offices and public 
areas, in HVAC vents, in elevator shafts, in the basement, and so on.
As for suppression mechanisms used, they can be based on water or on a fire suppression 
gas system. Water is common in human-friendly environments, whereas gaseous systems 
are more appropriate for computer rooms where personnel typically do not reside.