Choosing the "best" fire suppression technology is not a simple task. A good starting point is to discuss your risks and operations with your insurance carrier. The large insurance companies have consulting engineers available who will have direct experience with the various systems. Your insurance carrier has a vested interest in getting you the best possible advice.
The fire department's primary concern is life safety, not contents. Their interest in your suppression system relates to safe exit of staff and visitors. It must protect the structure from collapse, which would endanger the lives of the fire fighters. Protecting the contents is therefore the responsibility of the owner.
The starting point for choosing a fire suppression system is a risk analysis to reduce the potential for a fire. Many hazards can be eliminated or reduced. The second objective is to mitigate the damage and to facilitate the recovery effort associated with the type of suppressant used. Regardless of which system is chosen, quality of installation and maintenance is critical. Your insurance carrier can also assist with testing and maintenance procedures. The following is an overview of the common suppression systems:
Wet pipe - A well-designed system will include flow monitors and pressure gauges to monitor the pressure on both sides of the valves when closed. Once the pipe flange seals set after installation and the system is monitored and maintained, it is highly reliable. There are probably more wet pipe systems than any others. They have an excellent track record and of course fast response. As long as it is not a deluge system, heads release as needed at a predetermined temperature as the fire progresses. Wet pipe systems should be discharged monthly (to the outside through an external valve), and pumps, valves, pressure gauges and alarms verified at that time.
Dry pipe and pre-actioned dry pipe and combinations thereof are considered to require more maintenance than wet pipe. Corrosion is a problem in systems with air or nitrogen in the pipes. However, they do have a place in freezing environments. There is a slight delay before water gets to the head at the rated volume and pressure. As with wet pipe, flow and pressure monitoring will alert you to problems. The pre-actioned systems are activated by sensors, and water release can be total or zonal with the heads releasing from the heat of the fire. Pre-action systems rely on smoke detection to get the water into the pipes. If the detection monitoring fails, the system is not activated.
Both dry and wet pipe require that water be shut off manually.
Water mist systems are highly efficient but the technology is expensive. Small diameter piping is a plus and the use of a mist reduces damage to materials stored.
Fast response systems respond at an early stage of a fire. There are numerous types (release controls and heads) in this class of system.
Gas flooding systems are activated by temperature and smoke detection sensors. The gas is released under tremendous pressure. Statistics Canada is reported to have damaged certain records (shredded them) that were stored adjacent to the discharge nozzle. In computer rooms gas pressure is reported to have sent heavy floor tiles flying. These systems require that the room be extremely well sealed (doors, windows, ducts, piping, etc.) to achieve and hold the required concentration of suppressant. If the detection system fails there is no gas release. Should there be an equipment failure and the tank is discharged, there is no back-up. This is a major problem if the fire restarts itself. The length of time to get a tank recharged is a period of complete vulnerability.
Clearly the most important aspect of fire suppression is the sensing technology and monitoring (both technology and human, in-house and external). The next most important aspect after design is installation and maintenance. Every aspect of installation must be carefully monitored and inspected.
In one project, water pressure to sprinklers in a large records storage room was supplied by two 750 gal/min. pumps. The seals on the pumps were not evenly tightened during routine maintenance, which damaged the seals and the shaft alignment after about two years. Parts and repairs took almost one month for each pump. When a pump was out of service, there would have been an inadequate water supply to fight a major fire but sufficient for a small blaze. With shafts out of alignment, the pump might not have lasted long enough to combat a fire.
The pump and valve room should be well secured to avoid sabotage. Main supply valves should be locked open to avoid sabotage. Pumps require back-up power supply - another vulnerability.
At the end of the day there are no perfect solutions. You wrestle with options, choose one and accept the vulnerabilities. The protection of your structure, materials and people is reliant on good monitoring technology and safeguards, routine and thorough maintenance and a disaster recovery plan.
A good overview of fire suppression technologies is available in Chapter 4 of the recently published second edition of An Ounce of Prevention: Integrated Disaster Recovery Planning for Archives, Libraries and Records Centres, by Wellheiser and Scott. Scarecrow Press, Inc., ISBN 0-8108-4176-2.
Mark Hopkins is a Canadian information management consultant living in Trinidad, W.I. He has worked on both the planning and management of records storage facilities including high density storage systems. He can be reached at email@example.com.