| Fire can occur in a data center by either mechanical failure, intentional arson, or by natural causes, though the most common sources of fires are from electrical systems or hardware. Whether fire is measured in its threat to human life, damage to equipment, or loss of business due to disruption of services, the costs of a fire can be staggering. The replacement cost for the devastation caused by a fire can number in the tens or hundreds of millions of dollars. A fire can create catastrophic effects on the operations of the room. A large-scale fire can damage electronic equipment and the building structure beyond repair. Contamination from smoke and cinder from a smoldering fire can also damage hardware and incur heavy costs in cosmetic repairs . Even if the actual fire is avoided, discharge of the fire suppression medium could possibly damage hardware. Fire Prevention Several steps should be taken to avoid fires. Compliance with NFPA 75 will greatly increase the fire safety in the center. The following precautions should be taken in the design and maintenance of the data center and support areas: -
No smoking. Smoking should never be allowed in the data center. Signs should be posted at entryways and inside. If you think this could be a problem, designing in a nearby smoking area for breaks will reduce or eliminate smoking in the data center. -
No combustible materials. Keep flammable chemicals and combustible materials out of the data center. Store packing materials in a separate staging or storage area. -
Check HVAC reheat coils. Check the reheat coils on the air conditioner units periodically. If left unused for a while, they can collect dust that will smolder and ignite when they are heated up. -
Check suppression system. Sprinkler systems and/or FM200 fire suppression systems should be periodically checked. Also, they should be of a type triggered by heat, not smoke. -
Preserve the data center "cocoon." Periodically inspect the data center perimeter for breaches into more loosely controlled areas. Block any penetrations. An alarm or suppression system discharge caused by conditions outside the center is unacceptable. -
Have a disaster response plan. To maximize human safety and minimize fire damage, create a detailed disaster response plan. All data center personnel should be properly trained in the procedures, and the plan should be periodically reviewed. In an emergency, you might not be able to get into the building, so it is a good idea to keep a copy of the plan, along with a company phone list with home numbers , at the homes of several employees . -
Easy access to fire extinguishers. All personnel should know where extinguishers are and how to operate them. Physical Barriers The first line of fire defense and containment is the actual building structure. The rooms of the data center (and storage rooms) must be isolated by fire-resistant walls that extend from the concrete subfloor deck to the structural ceiling. The floor and ceiling must also be constructed of noncombustible or limited combustible materials able to resist the fire for at least an hour . Appropriately controlled firebreaks must also be present. The HVAC system should be dedicated to the controlled area of the data center. If this is not possible, appropriately rated fire dampers must be placed in all common ducts or plenums. Fire Detection Systems When data center fires occur, they are commonly due to the electrical system or hardware components. Short circuits can generate heat, melt components , and start a fire. Computer room fires are often small and smoldering with little effect on the room temperatures . The early warning fire detection system should have the following features: -
It should be a heat detection type. -
It should be installed and maintained in accordance with NFPA 72E, Standard on Automatic Fire Detectors . -
Each installation should be engineered for the specific area it will protect, allowing for air current patterns. -
Depending on local code, an automatic detection system might need to be installed under the raised floor, since electrical outlets are there. -
Since it can get very noisy in the data center, a visual alert, usually a red flashing siren light, should also be included in the system. Fire Suppression Systems A passive suppression system reacts to detected fire hazards with no manual intervention. The most common forms of passive suppression systems are sprinkler systems or chemical suppression systems. Modern gas systems are friendlier to hardware and, if the fire is stopped before it can do any serious damage, the data center might be able to continue operations. Water sprinklers are sometimes a viable alternative if saving the building is more important than saving the equipment (a water system will probably cause irreparable damage to the hardware). Gas systems are effective, but are also shorter lived. Once the gas is discharged, there is no second chance, whereas a water system can continue until the fire is out. Water systems are highly recommended in areas that contain a lot of combustible materials such as storerooms. These decisions must be weighed, but in the end it could be local ordinance, the insurance company, or the building owner who will determine what suppression system must be installed. There is no reason why multiple systems can't be used, if budget allows. Following are descriptions of a few different suppression systems. Note that the last two are not recommended, but are described in the event that such legacy systems exist in the facility. If either or both of these are in place, they should be changed out for safer systems. -
FM200. This is the recommended suppression system. The FM200 uses the gas heptafluoropropane which is quickly dispersed around the equipment. It works by literally removing heat energy from the fire to the extent that the combustion reaction cannot be sustained. It works quickly, is safe for people, doesn't damage hardware, won't interrupt electrical circuits, and requires no post-discharge cleanup. With this system there is the possibility that the data center will be back in business almost immediately after a fire. -
Dry pipe sprinkler. Dry pipe sprinkler systems are similar to wet pipe systems with the exception that the pipes are not flooded with water until detection of a fire threat. The advantage is less likelihood of leaks. The disadvantages are the longer amount of time before discharge and the possibility of ruining equipment. If this system is used, a mechanism should be installed that will deactivate all power, including power from UPSs and generators, before the system activates. -
Wet pipe sprinkler. Wet pipe sprinkler systems use pipes that are full at all times, allowing the system to discharge immediately upon the detection of a fire threat. The advantage is speed in addressing the fire. The disadvantages are the possibility of leaks and of ruining equipment. If this system is used, a mechanism should be installed that will deactivate all power, including power from UPSs and generators, before the system activates. -
Halon 1301. Not recommended. Halon is an ozone-depleting gas that has been replaced in favor of the more environmentally friendly FM200. Halon 1301 systems are no longer in production as of January 1994, and legacy systems can only be recharged with existing supplies . -
Carbon dioxide. Not recommended. Carbon dioxide is a very effective fire suppressant but is not safe for people. At the minimum design concentration as a total flooding fire suppressant (34 percent), carbon dioxide is lethal. At lower concentrations it can cause severe health problems. Manual Fire Suppression Manual means of fire suppression should also be on hand in the event that automatic systems fail. Following are descriptions of the two backup systems: -
Portable fire extinguishers. Portable extinguishers should be placed at strategic stations throughout the room. These should be unobstructed and clearly marked . Signs indicating the location of the extinguisher stations should be placed high enough to be seen over tall cabinets and racks from across the room. Tile lifters should also be located at each extinguisher station to allow access to the subfloor void, both for inspection and for addressing a fire. -
Manual pull stations. Manual pull stations should be installed at strategic points in the room. In areas where gas suppression systems are used, there should be a means of manual abort. In designs where it is necessary to hold the abort button to maintain the delay in discharge, it is essential that a means of communication be available within reach. Figure 11-1. Fire Extinguisher With a Highly Visible Sign  |
