CISSP Domain 3 Security Engineering – Part 3 – Perimeter Defenses Cheat Sheet

Types of Fire suppression agents

Always consult local fire code before implementing a fire suppression system.

All fire suppression agents work via four methods (sometimes in combination): reducing temperature of fire, reducing supply of oxygen, reducing supply of fuel, and interfering with the chemical reaction within fire.


Water suppresses fire by lowering the temperature below the kindling point (ignition point). Water is the safest of all suppressive agents, and recommended for extinguishing common combustible fires such as burning paper or wood. It is important to cut electrical power when extinguishing a fire with water to reduce the risk of electrocution.

Soda Acid

Old giant brass fire extinguishers use soda acid (Sodium Bicarbonate, mixed with water and acid to create a gas). It suppresses fire by lowering temperature, it creates foam that can flow on the surface of some liquid fires, starving oxygen supply.

Dry Powder

Contains sodium chloride and works by lowering temperature and smothering the fire, starving it with oxygen. Dry power is used primarily with metal fires (sodium, magnesium and others)

Wet Chemical

Used to extinguish kitchen fires (type K in US and type F in Europe) and can be used for common fires (type A). It contains potassium acetate mixed with water. It is used to cover the grease or oil in a fire with a soapy film that lowers the temperature.


Suppresses fire by removing oxygen. It’s a dangerous suppressive agent, as it is oderless and colorless causing person that breathe them in to suffocate due to lack of oxygen. Therefore it is only recommended for use in unstaffed electrical substations. All persons entering CO2 protected areas should be trained for safety; safety controls such as oxygen tanks are recommended.

Halon and Halon Substitutes

Extinguishes fire via chemical reaction that consumes energy and lowers the temperature of the fire. Compared to CO2 it is safer as systems are designed with enough oxygen to support life.

Montreal Accord (Protocol)

Halon has ozone depletion properties. Production and consumption is banned in developed countries. There are exceptions for certain critical uses such as in airplanes or submarines. Halon is no longer recommended due to age. Most systems are 20 years old and are due to be replaced.

Halon Replacements

  • Argon – safe up to 15% concentration
  • FE13 – newest and safest – can be breathed in concentrations up to 30%
  • FM-200 – safe up to 15% concentration
  • Inergen – safe up to 15% concentration

Count-down Timers

CO2, Halon and Halon substitutes such as FM200 are gas based system which require countdown timers (both visible and audible) before gas is released. For safety reasons this allows personnel to evacuate before release as well as allows them to stop the release incase of a false alarm.

Water is usually the recommended fire suppression agent. Water in the absense of electricity is the safest suppression agent for people

Sprinkler Systems

Often combined with fire alarm that alerts people to evacuate the premises in case of fire.

Wet Pipe

Wet pipes have water right up to the sprinkler heads: the pipes are “wet”. The sprinkler head contains a metal or a small glass bulb designed to melt or break at a specific temperature enabling water to flow. Bulbs comes in different colors indicating different trigger temperatures; Orange (57C), Red (68C), Yellow (79C), Green (93C).

Dry Pipe

Dry pipe systems have closed sprinkler heads; the difference is the pipes are filled with compressed air. The water is held back by a valve that remains closed as long as sufficient air pressure remains in the pipes. As the dry pipe sprinkler heads open, the air pressure drops in each pipe, allowing the valve to open and send water to that head. Dry pipes are often used in areas where water may freeze, such as parking garages.


Similar to dry pipes, except the sprinkler heads are open and larger than dry pipe heads. The pipes are empty at normal air pressure; a deluge valve holds the water back. The valve is opened when a fire alarm (the may monitor smoke or flame sensors) triggers.


Combines wet, dry or deluge system and require separate triggers to release the water. Single interlock systems release water into the pipes when a fire alarm is triggered. The water releases once the head opens. Double interlock systems used compressed air (same as dry pipes); the water will not fill the pipes until both the fire alarm triggers and the sprinkler head opens. Pre-action systems are used in areas such as museums, where accidental discharge would be expensive. Double interlock systems are used in cold areas such as freezers to avoid frozen pipes.

Portable Fire Extinguishers

All portable fire extinguishers should be marked with a the type of fire they are designed to extinguish. They should be small enough to be used by any personnel.
Use PASS method to extinguish fire with a portable fire extinguisher.

  • Pull the pin
  • Aim low
  • Squeeze the pin
  • Sweep the fire
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About the Author

Alfred Tong
Author and owner of this blog. A Networking enthusiast, full time networking and systems Engineer. Generally curious about all things IT.Certifications: GIAC GSEC, CCNP-S, CCNP, CCSP, CCDP, CCNA, RHCE, JNCIA - FWV