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Suppression of Fires Exposed to an External Radiant Flux.


pdf icon Suppression of Fires Exposed to an External Radiant Flux. (23893 K)
Donnelly, M. K.; Grosshandler, W. L.

NISTIR 6827; 29 p. December 2001.
Order number: PB2002-103179

Keywords:

fire suppression; radiant flux profile; cup burner; cleaning agents

Abstract:

When materials are burning in the presence of a continuous, external energy source, they are often more difficult to extinguish and may require an increase in suppression agent concentration to extinguish the fire. This situation could exist for class C fires involving electrically energized wires that cannot be de-energized. There is a need for data to determine what increase in extinguishing agent concentration is necessary when the external energy source cannot be powered off. In response to this, a Radiant Enhanced Extinguishing Device (REED) was developed to examine the amount of agent necessary to suppress the fire as a function of the flux from an external energy source. The design for the REED is based on the design of the standard cup burner apparatus identified in the NFPA 2001 Standard on Clean Agent Fire Extinguishing Systems (NFPA, 2000). While the cup burner is designed for use with liquid or gaseous fuels, the REED tests solid fuels. Five fuel materials were tested: poly methyl methacrylate (PMMA), polypropylene, acrylonitrile butadiene styrene (ABS), polyvinyl chloride (PVC), and ethylene propylene diene monomer (EPDM). Nitrogen was used as the suppression agent for all of the materials tested. The results showed that the amount of agent needed to suppress the fire increased as the radiant flux on the fuel increased. In some cases, the amount of suppressant needed reached a plateau for the flux levels tested. For the materials evaluated, the amount of nitrogen needed to extinguish the sample at the higher heat fluxes was greater than the heptane cup burner value for nitrogen. The results demonstrate the impact extra radiant energy can have on extinguishing a fire, and the need for data to predict how much extra agent to use in these situations. The REED apparatus provides a method for collecting suppression data for fire exposed to an external flux.