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Comments on "Correction Factors for the Heat of Combustion in NFPA 72 Appendix B".


pdf icon Comments on "Correction Factors for the Heat of Combustion in NFPA 72 Appendix B". (2741 K)
Davis, W. D.

Fire Protection Engineering, No. 4, 46-48, Fall 1999.

Keywords:

ceiling jets; fire models; experiments; heat detection; heat of combustion; NFPA 72

Abstract:

I want to express some reservations concerning the revision to NFPA 72 Appendix B that is being considered based on an article by Christopher E. Marrion in Fire Protection Engineering. The rationale for this revision is based on a paper published by Heskestad and Delichatsios in which the correlation (H&D) used in NPPA 72 Appendix B was modified due to an updated measurement for the heat of combustion of sugar pine. The revision is substantial in that the heat of combustion for sugar pine is reduced by a factor of 1.67 which significantly changes the relationship between convective heat release rate and excess temperature at the ceiling. Changes such as theses, which substantially impact the way fire protection engineers perform detector placement analysis, should be verified using independent supporting experiments in order to avoid dependence on a single investigation. Heskestad and Delichatsios were very careful in their original paper to compare their measurements with existing experimental data in order to verify that the results were supported with comparable experiments. In their revision, when the heat of combustion was changed, no comparison was made to the results of other experiments.