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Fires can be one of the most common and devastating risks to facilities. There are 3 aspects you must be aware of.

Fire Prevention

Fire prevention includes both proper construction and employee training, both subjects which have already been covered in detail.

Fire Detection

Fire detection is really all about detecting the environmental changes due to fires – smoke and heat. Computer equipment normally does not use enough voltage to start a fire on its own – if a fire starts, it will usually be because of overheated wire insulation or by plastic that ignites as a result of overheated components. In either case, there will probably be a decent amount of time in which there is smoke before the fire actually ignites – that is why smoke detection is so important.

There are 2 types of fire detectors. The first, smoke activated, is a photoelectric device which detects a change in light intensity. It shines a very narrow beam of light across a detector, and if the light is obstructed by smoke, an alarm sounds. Some devices will draw surrounding air into the device in order to provide a faster reaction time. The second type of fire detection is called heat activated, and as the name implies, detects when there is a rise in temperature. These detectors come in two flavors – fixed temperature and rate-of-rise. Fixed temperature detectors will trigger an alarm when the temperature reaches a specific value, while rate-of-rise detectors detect a change in temperature over time. Rate-of- rise detectors raise the alarm quicker, but can also provide more false positives.

Detectors should be installed above and below dropped ceilings and in raised floors as well. They should also be installed in enclosed spaced and air ducts as smoke can gather in these places without traveling to other areas.

Fire Suppression

There are five classes of fires – A, B, C, D and K – we will cover them in just a second. For now, it is important to know that fire extinguishers are well-marked to indicate the types of fires that extinguisher can be used on as well as to the contents. Portable fire extinguishers should be located within 50 feet of electrical equipment as well as near exits, and should be inspected quarterly.

Suppression agents are usually automated systems that engage when a fire is detected and act to extinguish the fire. Each agent has a coverage zone and the chemical used will differ based on the excepted type of fire as well as the contents of that zone. It is important to know the five different types of fires, as using the wrong type of chemical may make the fire significantly worse.

First of all, let’s discus what fire is. You may think you know fire, but what would you think if I told you that it really does not exist? Well, it does not. What we typically think of as fire, or flames, is really just the byproducts of a chemical reaction under high heat floating away. The crucial ingredient for ‘fire’ is O2, or oxygen. Under high heat, oxygen reacts with just about any material, and the result is the destruction of the material. The material is the fuel for the fire, so any fire requires three things – fuel, oxygen and lots of heat. Taking away even one of those ingredients will stop a fire. Again, fire is just oxygen reacting with the fuel when high temperatures are present.

Let’s discuss the types of chemicals used for extinguishing fires. First of all, there is good old H2O, or water. How would that put out a fire? By removing the heat – water cools down the fuel, and if we can cool it down enough, the fire goes out.

Then we have foam, which is usually just water mixed with a foaming agent to allow it to float on top of a burning substance. This acts in two ways – first it can cool down the fuel, but more importantly it smothers the fire – it creates an airtight barrier on top of it and robs the fire of oxygen.

Carbon Dioxide, or CO2, also puts out a fire by robbing it of oxygen – it will actually remove oxygen from the air. Unfortunately, CO2 is an odorless, colorless gas and is equally good at smothering people as it is in smothering fires. Therefore it is usually only used in unattended facilities. If it is used where people might be, it should be configured to activate a few minutes after alarms start sounding to allow people to exit the area.

Then we have gases. We used to use Halon, which simply prevents the chemical reaction from taking place - leaving the fuel and oxygen, and the high heat eventually dissipates. However, due to the negative effects halon has on the ozone layer, it has not been manufactured since 1992. The best replacement is FM-200 which works in the same manner.

We have dry powders to fight fires. There are different dry powders we can use, and each acts in one of two ways. Sodium bicarbonate, potassium bicarbonate or calcium carbonate act like FM-200 and prevent the chemical reaction from occurring. Monoammonium phosphate simply deprives the fire of oxygen.

Lastly we have a wet chemical, usually containing potassium acetate, which is designed to put out oil fires, such as are commonly found in kitchen fires.

Now let’s discuss the 4 types of fires and what suppression technique should be used for each. Class A fires are the most common and result from the ignition of wood, paper or laminates. These are easily put out by water or foam, which remove the high heat.

Class B fires are caused when some type of liquid – such as gasoline – catch fire. Water will not do us any good here, since these types of liquids will normally not mix with water. In these cases we need to use gas, CO2, foam or dry powders. Basically just about anything except water. While foam is usually water-based, it can still work because it will lay on top of the fuel and deprive it of oxygen.

Class C fires are fires in electrical equipment or wires. While water could put these fires out, water conducts electricity, and so the cure could be much worse than the disease. A better solution is gas, CO2, or dry powders. Since foam is water-based, it is not a good idea either.

Class D fires result from the ignition of combustible metals such as magnesium, sodium or potassium. These types of fires usually burn extremely hot and can only be tamed by using dry powders.

Class K fires are specific to commercial kitchens, which are usually cooking oil fires. They should be addressed using wet chemicals.

Since the most common fire is Class A, and water is best method for extinguishing those fires, it is very common to see water sprinklers extruding from ceilings. The downside of sprinkler systems is that they can cause water damage and the fact that any live electricity can either make the fire worse or cause harm to people. Therefore it is important that electricity be cutoff before water sprinklers are allowed to activate. 4 main types of water sprinklers can be installed.

• Wet Pipe – pressurized water is always in the pipe leading to the sprinkler head and activate when elevated temperatures are detected; susceptible to burst pipes in freezing weather

• Dry Pipe – same as a wet pipe, but the pipe leading to the sprinkler head contains air pressure which keeps the water in a central storage tank until elevated temperatures are detected

• Precaution – same as a dry pipe, but before the sprinkler head is activated, a thermal-fusible link on the sprinkler head must melt; this gives people time to handle the fire manually and is

commonly used in data centers

• Deluge – allows a massive amount of water to be released instead of ‘sprinkled’; not used in data centers

One last note – even though we covered this in the Asset Security domain, plenum space is the area under raised floors and lowered ceilings where power can data cabling can be run. Plenum-rated cabling should be used in these areas as they used materials that will not produce toxic fumes when burning.

Fire Class Material Suppression

A Common Water, foam

B Liquid

Gas, CO2, foam, dry powders

C Electrical Gas, CO2, dry powders D

High-temperature

chemicals Dry powder

K Cooking oils Wet chemicals

Fire Classes and Suppression

Communication and Network Security Domain