Fire Safety Science Digital Archive

A generalized relationship is presented for determining air flow rates through narrow gaps around door edges. The relationship provides values of leakage rates for steady, laminar flow through gaps over a wide range of pressure difference and eliminates approximations associated with the often inappropriate use of discharge coefficients and exponents in the flow equation Q = C A(?p)". The analysis covers straight-through, single bend and double bend gaps of constant thickness, as well as connected gaps of constant thicknesses. Comparison of measured flow rates for installed stairwell door assemblies with those predicted by use of the relationship shows agreement within 20 percent. The volumetric flow of heated air through simple door gaps has been calculated by use of the relationship. The results show that the flow rate may increase or decrease with temperature depending on gap size and flow region.