Volume 15, Number 2, May 1993, pp.34-36
Museum and library management is entrusted with the critical responsibility of protecting and preserving their institution's collections, operations, staff, and mission. Constant attention is required to minimize adverse impact due to humidity, temperature, theft, vandalism, decay, and fire. Of these, fire constitutes the most serious concern because of the speed and totality of its destructive forces. Vandalized or environmentally damaged objects can be repaired and stolen objects recovered. Fire-destroyed items are gone forever.
Automatic fire-suppression systems, designed to rapidly identify and extinguish a developing fire, are often provided museums and libraries. Several suppression options are available which utilize water or one of the various gas agents.
In cultural institutions, systems utilizing Halon 1301 gas have been one of the preferred suppression options. Halon 1301 is a colorless, odorless, and non-toxic gas which extinguishes the fire by chemically reacting with the combustion process. It does not leave a residue which can harm collections or other contents and does not require extensive clean up. As such, this agent has been a choice fire-extinguishing method in museums, especially where water damage is a concern.
While desirable, Halon 1301 is now known to be environmentally damaging, particularly toward the earth's protective ozone layer. As a result, production of this gas has, or will be, ceased within the next year. Museums, libraries, and other culturally significant organizations will legally be able to continue purchasing replacement Halon 1301 gas. Prices, however, will become substantially higher as reserve supplies are used and as federally mandated environmental taxes are added. Halon gas, which cost approximately $7-$10 per pound in 1985, is expected to cost $80-$100 per pound by the year 2000. For a typical protected room with 1000-5000 pounds of gas, the system recharge cost will be prohibitive.
Like all other Halon 1301 system users, cultural institutions must closely evaluate continued use of their Halon 1301 systems and decide whether system use should continue or an alternative protection method is to be selected. This paper will provide the basic fire-suppression options available for museum management.
Present halon systems will continue to offer fire protection.
Advantages include an initial expenditure savings since modification work is not necessary, as well as the fire fighting benefits offered by halon.
Disadvantages include the fact that most halon systems offer only one opportunity to extinguish the fire due to the limited gas storage. Should fire re-ignition occur, severe loss is probable. Halon systems have one of the most expensive fire-suppression system maintenance costs. Another disadvantage is that replacement gas will be difficult to obtain and/or expensive should a halon discharge occur.
A constant observed problem in Halon 1301-protected rooms is the lack of adequate system and room maintenance, particularly with respect to maintaining air-tight room seals. Halon 1301 is a heavier-than-air gas. The protected room must remain air tight or the gas will flow to other parts of the building, preventing proper fire extinguishment. Open doors and holes in floors and walls are culprits. This situation exists in more than 50% of the halon-protected rooms showing deficiencies.
This solution involves deactivation of the halon-release
equipment, preventing halon discharge into the room.
Not a recommended option.
Advantages include prevention of environmental impact and little modification cost. Existing detection equipment can continue to function.
Disadvantages include the fact that this option does not deal with the basic issue of protecting the museum and its collections from fire loss. Should fire outbreak occur, a high probability exists for severe or total collection loss. Insurance expenditures may also increase due to the lack of risk protection.
Other environmentally non-damaging gases such as carbon dioxide are available for fire suppression. This option would involve replacing halon with one of the alternative gases.
Advantages include avoidance of water damage from extinguishing operations and the continued use of existing Halon 1301 detection and control equipment.
Disadvantages include the possible need for extensive pipe modifications due to differing agent flow factors and health hazards associated with some gases. Carbon dioxide, for example, inerts the atmosphere making human breathing impossible.
These gases are not recommended where people may be present.
Halon manufacturers are attempting to develop alternative extinguishing agents to replace Halon 1301. The date and characteristics of these gases are yet unknown to the general community.
Possible advantages include the continued benefits of Halon 1301.
Possible disadvantages include expected differing flow characteristics, mandating pipe modifications to existing systems. The toxicological effects of these alternative gases are unknown, which may prohibit use in human occupied rooms.
As a side note, "halon" is a generic term for any of the extinguishing gases containing chemical elements of the halogen series. These elements include chlorine (Cl), fluorine (F), iodine (I), and bromine (Br). It will be important for conservators and preservation staff to determine whether or not these new agents can chemically damage fine art pigments or other collections.
Several large halon users are suspect of replacement gases and have decided to replace halon systems with automatic fire sprinklers. As several of these organizations have discovered, the health safety of water is already known.
This solution would involve removal of the halon system and replacement of protection with a quick-response, automatic, wet- pipe sprinkler system. Sprinklers are individually operated, heat-activated devices. Contrary to popular belief, the activation of one sprinkler does not cause all sprinklers to operate. Approximately 85% of all fires are controlled with 1 or 2 sprinklers.
Advantages include the statistic that wet-pipe sprinkler systems are the most reliable and safest fire extinguishing method available. Sprinkler systems are relatively easy to maintain and modify, saving facilities expenditure. Smoke detection equipment can provide early warning of a developing fire, permitting manual suppression opportunity prior to sprinkler activation. The environmental and human safety aspects of water is known, unlike possible impact from the various chemical agents. Recovery techniques for water-damaged materials are also known.
Disadvantages include possible high initial installation expenditures to install the new system. Water clean up and restoration efforts will be necessary following discharge. The volume of water is, however, relative: the average sprinkler discharges 15-20 gallons per minute while typical fire hoses release 120-250 gallons per minute. It is also important to remember that water damage is often repairable while fire damage is not.
The use of fire sprinklers in museums has traditionally been avoided, largely due to fears of accidental sprinkler discharge. While understandable, these fears are statistically unfounded. The industry wide sprinkler failure rate in all occupancies, including industrial and warehousing, is 1 sprinkler per 16,000,000 installed per year. In museum applications, sprinkler failure is almost unheard of. This is due to the testing procedures used by manufacturers which cause defective sprinklers to fail in the factory rather than in application.
Currently several premiere cultural heritage institutions have, or are in the process of installing, complete automatic sprinkler protection. Examples include the Library of Congress, the Smithsonian Institution, the National Library and Archives of Canada, and the National Library of Scotland.
Wet-pipe automatic sprinklers represent the most effective alternative for typical museum and library fire-suppression objectives.
This solution would involve removal of the halon system and replacement of protection with a automatic, dry-pipe sprinkler system. Dry-pipe systems are essentially the same as wet-pipe systems except that the pipes in the protected area contain pressurized air. The air holds a valve closed which in turn prevents water from entering sprinkler piping. When a sprinkler head operates from a fire, the system air is released and water flow occurs. Dry systems are suited for locations subject to freezing.
Advantages include the sprinkler protection benefits indicated under the wet-pipe systems.
Disadvantages include the higher installation and maintenance expenses associated with dry-pipe systems, especially when compared to wet-pipe systems. A longer sprinkler response time during the critical first moments of fire is possible due to the time required for the water to travel from the control valve to the open sprinkler head. Response time may lag by as much as 1 minute, allowing a larger number of sprinklers to operate.
In museum applications, dry-pipe sprinkler do not offer any significant advantage over wet systems.
This option involves replacement of the halon protection with a pre-action type sprinkler system. The principle of pre-action is that the piping in the protected area is dry. Water is held back by an electronic pneumatic valve, controlled by the room's detection system. Upon detector operation, water is introduced into the piping. When the sprinkler head operates, this water is discharged onto the fire.
Advantages include the sprinkler advantages presented under Option 5. Another advantage is that two independent actions are necessary to release water: a detector operation and sprinkler head activation.
Disadvantages include a longer sprinkler response time in fast- developing fires and increased installation and maintenance expenditures due to increased system complexity.
An emerging fire-sprinkler technology which holds high promise for water-sensitive applications is the water mist system. Water mist sprinklers will deliver water at exceptionally high pressures, producing a fine, high-efficiency water vapor. This will maximize water's cooling capacities, thereby extinguishing fires with minimal amounts of water. Experimental tests to date have shown that many room fires can be controlled with as little as 2-3 liters of water. Extinguishing system operation will be controlled by one of the highly reliable sampling smoke detection systems like VESDA. (VESDA--Very Early Smoke Detecting Apparatus--is an air-sampling smoke-detection system that collects and analyzes room air conditions and identifies incipient fire development. It will typically detect a fire condition prior to visible smoke).
Advantages include the sprinkler advantages presented under Option 5. The other major advantage will be the minimal resultant water damage and clean up effort.
The main known disadvantage of this technology is that it is still a few years away from practical use. Therefore, buildings which are currently unprotected will have to remain so until mist sprinklers are fully developed. In addition, mist system capabilities and constraints are not fully known. These systems may not be effective for all museum and library applications.
In general, water mist systems are expected to offer a significant fire suppression option for many cultural heritage applications.
Environmental issues are causing an inconvenience for halon protection. Ultimately, however, these inconveniences are not necessarily bad for museums. Opportunity exists to install correct, alternate protection systems within the museum's best interest. Several automatic fire suppression options exist for museums and libraries. For most applications the best choice still remains a properly designed, installed, and maintained wet-pipe automatic sprinkler.Nicholas Artim
about the author:
Nicholas Artim is director of the Fire-Safety Network in Needham, Massachusetts. He has extensive education and experience in fire protection technology. He designed, installed, and maintained fire protection systems for the U.S. Capitol, U.S. Supreme Court, The Library of Congress, and the U.S. Congressional Office Buildings, and he is participating in fire protection analysis and solution development for the National Gallery of Art (Washington, D.C.), The National Library of Canada (Ottawa), the National Archives of Canada, National Library of Scotland, National Galleries of Scotland, and other repositories of cultural materials.