Bhushan Lohar

The United States Air Force (USAF) dictates policy for foam fire suppression systems in their hangars. In November 2021, the USAF issued a Sundown Policy for Foam Fire Suppression Systems. The National Fire Protection Association’s Standard on Aircraft Hangars, NFPA 409 serves a similar function. This article uses a real-world installation and analysis of the hangar fire protection scheme stipulated in the USAF Sundown Policy as compared to an installation in compliance with NFPA 409. Applying the Poisson process for a zero-inflated probability distribution, the data referenced for the event tree were evaluated and thereafter validated. The analysis shows that the installation of hangar fire protection stipulated in the USAF Sundown Policy achieves a better performance for the fire protection system than an installation in compliance with NFPA 409, insofar as the risk analysis is concerned. Second, the installation of a fire protection system that complies with the requirements of NFPA 409 fails to achieve the basic probabilistic performance promulgated by the International Code Council’s Performance Code (ICCPC). The validation also demonstrated that the scenario involving the accidental discharge of fire foam was significantly more likely to occur compared to that involving only fire occurrences.