On the Significance of Transient Heat Release Rate Excursions Above a Set Limit.
On the Significance of Transient Heat Release Rate
Excursions Above a Set Limit.
Ohlemiller, T. J.; Peacock, R. D.
Fire Safety Journal, Vol. 43, No. 8, 531-540, November
heat release rate; furnishings; ignition; fire hazards;
methodology; smoke layers; furniture; NFPA 555; room
When a heat release rate limit for a consumer product is
set by a regulatory agency, it is of interest to know
whether small excursions above that limit, such as may
occur due to production line variability, represent a
disproportionate increase in fire hazard. This paper
presents a methodology to examine this issue. The heat
release rate curve of the object is described by a
Gaussian time variation; a perturbation peak, also
Gaussian, is added to this main peak. The impacts of the
perturbation peak on the build up of hazardous
conditions in a room fire (where the object is the only
item burning) and on the threat of ignition of secondary
items are examined. For the peak heat release rate
domain studied here, only the ignition threat is
significantly affected by the perturbation peak. The
results quantify the trade-off between the height of the
perturbation peak and its duration for a fixed
percentage of increase in the room area threatened by
secondary object ignition. The results show that the
increased threat is of the same order as the relative
perturbation in heat release rate.