WAACNewsletter
Volume 17, Number 3 .... September 1995

An Update on Micromist Fire Extinguishment Systems

by Nick Artim

A description of micromist fire extinguishment systems appeared in Section 7 of An Introduction to Automatic Fire Sprinklers by Nick Artim, which ran as two parts in the WAAC Newsletter: September 1994, vol. 16, no. 3; and May 1995, vol. 17, no. 2. For those who may have missed it, an exerpt of the section follows.

Water Mist

One of the most promising extinguishing technologies involves the use of fine water droplets, known as micromist.

This technology represents a potential solution to the protection void left by environmental concerns, and subsequent demise of Halon 1301 gas.

Micromist systems discharge limited water quantities at very high release pressures (approximately 1,000 psi). This produces droplets of less than 20 microns diameter, resulting in exceptionally high efficiency cooling and fire control with significantly little water. Initial system tests have demonstrated successful fire extinguishment in hotel room scenarios, mockup library bookstacks, computer rooms and underfloor cable spaces. In most situations these fires have been extinguished with 1-5 gallons of water. Many of the test scenarios have been suppressed in less than 1 minute, with all fire scenarios extinguished within 5 minutes. Water saturation, often associated with standard firefighting procedures, is avoided. Other anticipated micromist benefits include: lower installation costs, minimal aesthetic impact, and known environmental safety.

The Newsletter is pleased to provide an update on latest studies of this intriguing system courtesy, as always, of Nick Artim.

The water mist system has successfully completed a series of tests on fixed library stackage systems. These tests were performed on a stack arrangement similar to the Library of Congress rare book vaults. The results have been very encouraging, demonstrating substantial fire extinguishment with a maximum of 10% of the water discharge which would occur in a normal sprinkler controlled fire. Tests on standard hotel guest rooms, which have a fuel loading comparable to exhibition rooms in many historic houses, have also established a high degree of confidence.

The system is now in final preparation to Underwriter's Laboratories for listing submittal on or about July 1, 1995. Initial system listing will be for an ordinary combustible space of 1,000 sq. ft., which is a starting point. Subsequent listings for larger spaces will immediately follow. Concurrently, there will also be a special listing for fixed library shelving protection. This listing process takes approximately 4-5 months. Therefore, the first listings are expected in late 1995.

At the same time work is progressing at the Library of Congress where a mist unit has been set up in the fumigation vault of the John Adams building. Here, LOC preservation and conservation personnel, as well as conservators from the National Gallery, National Park Service, and National Archives will continue to study the non-thermal impact of mist. These studies are designed to establish any necessary recovery efforts, and optimal storage arrangements for collections in mist protected spaces. Some of this information is actually being submitted to UL so that the listing organization's people can gain a detailed understanding of the system's objectives.

Two beta test sites have been established in order to study several site installation details. Tests will involve the engineering staff of each system component manufacturer (Reliable, Fire Control Instruments, Baumac, and IEI), each test institution's staff including building conservation and management, and myself as the application engineer. At each site a system will be designed and installed to evaluate application methodologies, identify any necessary minor component modifications, and assemble installation documentation.

The two selected sites are the Library of Congress and Jefferson rare book vaults, at Canterbury Shaker Village, Canterbury, New Hampshire. One site represents a large urban institution in a constant climate controlled situation, while the other is a rural facility with little available fire- fighting water and which is subject to weather extremes. Design of the two systems has begun in anticipation of the listing.

Testing by the University of Maryland, Department of Fire Engineering is continuing for a variety of scenarios including office and residential rooms, computer underfloor spaces, telecommunication mainframes, and mocked up aircraft cabins.

Based on the overwhelming success of the library fixed stack series, a number of tests will be performed on compact mobile shelving systems. Compacts represent very severe fuel loads in many heritage properties. When they catch fire, extinguishment is difficult, requiring exceptionally high quantities of water. We feel that it is possible to engineer a mist system into the compact carriages which can extinguish a fire with approximately 1/50th the normal quantity of water. The National Library of Canada has sent a number of compact units to the Maryland site for these tests.

We are also working with the National Park Service, North Atlantic region to identify issues associated with developing a technically appropriate mist system for historic houses. A series of tests are planned for this summer at Minuteman National Historic Site, Concord, Massachusetts. These tests will involve product component manufacturer's, NPS regional architects and engineers, several NPS site superintendents, and fire officials.

Again, additional information will be forthcoming as it is developed.

Nick Artim is the Director of Fire Safety Network, Middlebury, Vermont.

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