Establishing a safety factor for the distribution density of compressed-air foam and evaluating CAF's extinguishing performance on free-flowing spill fires

Compressed-air foam (CAF) has been proven to be an effective fire suppression material for both class A and B fires. Comparison testing between CAF and standard foam water sprinklers had been conducted previously to quantify the amount of CAF required to outperform a foam water sprinkler system in extinguishing a liquid fuel pan fire and provide superior burn-back protection as specified in the UL162 Foam Equipment and Liquid Concentrates standard. Concerns about variations in the delivered CAF density due to fluctuating water supply pressures and its performance on actual spill fires have been raised in the industry. This paper describes a series of full-scale Class B fire tests designed to address these concerns. Tests were conducted, using the fire test method described in the UL162 Foam Equipment and Liquid Concentrates standard, to establish minimum and maximum delivered densities of CAF by varying the water supply pressures. A safety factor could then be associated with the normal design application density. Tests were also conducted on a 6 m by 6 m poured concrete slab to compare CAF and standard foam water sprinklers in extinguishing free flowing heptane spill fires with and without shielded areas. These fires ranged in size from 4.65 m2 to 13 m2.
Symposium on Advances in Fire Suppression Technologies, October 1, 2005, San Diego, CA.