Effectiveness of Fire Extinguishing Powders Based on Small Scale Suppression Tests.

摘要

A simple laboratory test method was developed for evaluating the fire extinguishing power of dry chemical agents. The apparatus consisted of a Bunsen burner which was modified by the addition of a delivery tube to permit the dry chemical powder to be injected into the methane/air stream about 4 cm below the burner tip. The powder concentration was increased until the test flame was extinguished. A total of 21 commercial extinguishing powders were tested in this apparatus. It was found that the fire extinguishing effectiveness of a given powder is primarily determined by its particle size rather than its chemical composition. For four of the agents tested (KHCO3,NH4H2PO4, KCl and NaHCO3), it was found that the fire extinguishing performance could be divided into three regions: (1) a very effective range up to 25 micrometers, (2) a transition range with a steep effectiveness slope in the 25-50 micrometers particle size range, and (3) relatively ineffective range above 50 micrometers. The same type of behavior was found for Monnex(TM) except that very effective range extended to about 40 micrometers and the transition range was 40-60 micrometers. jg p.3.