(120c) Effects of System and Agent Properties on Room Pressurization

Since the 1987 mandated phaseout of Halon 1301 by the Montreal Protocol, many alternative fire suppression agents have been introduced into the marketplace by a variety of manufacturers. The primary design focus with regards to the hazard enclosure, using these alternate agents, has been related to limiting enclosure leakage. Much research and data exists for how to design and test a hazard enclosure to minimize the enclosure leakage and obtain the 10 minute agent hold time as mandated by NFPA 2001. However, until recently, little testing or research had been conducted on the overall effects of these various agents and agent delivery systems on the enclosure pressure during the discharge of the agent. Especially with the expanding use of high-pressure inert gas systems in the United States, the topic of room pressurization has begun to move to the forefront in the minds of system designers and manufacturers. Per NFPA 2001, the burden of determining the proper enclosure venting scheme to reduce potentially hazardous room pressures falls on designers who must ultimately rely on the individual manufacturers. This has lead several of the largest system manufacturers to collaborate to evaluate the effects of a variety of variables including agent type, enclosure humidity, vent area and delivery system on the room pressurization. This testing has helped to establish those effects and aided in developing guidelines to deal with those effects. These tests were conducted during two separate week-long visits to the fire test facility at Fike Corporation in Blue Springs, Missouri. The test enclosure used was a 100 m3 (3531 ft3) enclosure designed to meet the fire test enclosure requirements of Underwriters Laboratories (UL), Factory Mutual (FM) and International Organization for Standardization (ISO). Room pressure, both positive and negative, nozzle pressure and relative humidity measurements were obtained for each test scenario.