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Assessment of the Fire Performance of School Bus Interior Components. Final Report.



E Braun, S Davis, J H. Klote, Barbara C. Levin, M Paabo


Since seat assemblies represent the single largest type of combustible fuel in a school bus interior, this study is limited to currently used and state-of-the-art material assemblies. Six different seat assemblies having a range of fire performance were examined. Small-scale tests (Cone Caloimeter, LIFT, and NBS Toxicity Protocol) were performed on these materials. Large-scale tests (Furniture Calorimeter) were conducted on single seat assemblies. Full-scale tests were performed using a simulated bus enclosure measuring 2.44 m wide by 2.13 m high by 8.23 m long and three seat assemblies. The impact of ignition source size was determined by computer simulation. It was found that a 500 kW ignition source could produce untenable thermal conditions in the simulated bus enclosure. Seat assemblies were exposed to 50 kw and 100 kw ignition sources in the large-scale tests and 100 kW ignition source in the full-scale tests. It was found that the small-scale tests were unable to provide a simple method for material selection that was consistent with the full-scale test results. At the present time, small-scale fire tests of materials cannot be depended upon to predict the fire behavior in the real world. Therefore, based on the full-scale test results, a generalized full-scale test protocol for seat assembly evaluation was developed that combines full-scale testing in an enclosure with an analysis protocol that determines the time-to-untenable conditions. The procedure defines the conditions under which toxicity testing would be necessary. Full-scale test instrumentation and material orientation are also described.
NIST Interagency/Internal Report (NISTIR) - 4347
Report Number


buses, cone calorimeters, seats, flame spread, furniture calorimeters, combustion products, smoke, tenability limits, toxicity, large scale fire tests, small scale fire tests


Braun, E. , Davis, S. , Klote, J. , Levin, B. and Paabo, M. (1990), Assessment of the Fire Performance of School Bus Interior Components. Final Report., NIST Interagency/Internal Report (NISTIR), National Institute of Standards and Technology, Gaithersburg, MD, [online], (Accessed June 16, 2024)


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Created July 1, 1990, Updated November 10, 2018