Citation

Marshall NR. Fire Safety J. 1988; 13(2-3): 155-162.

Copyright

(Copyright © 1988, Elsevier Publishing)

DOI

unavailable

PMID

unavailable

Abstract

Many recent experimental and test systems for measuring the quantity of smoke produced from burning materials have used a hood to collect the smoky gases, which are then ducted past the measuring instruments. It is known that these instruments have been variously located between 2 and 20 duct diameters from the entry.Where the intention is to measure a bulk or average property of the smoke, it is best to locate the measuring instruments far enough along the duct for the gases to have homogenized.An experiment using a 1/6 scale hood and duct, carried out at the U.K. Fire Research Station has shown that buoyant gases will homogenize to within 1% in a square vertical duct by 12.5 duct widths.It has further been demonstrated that, for this hodd and vertical duct the height at which gases achieve this homogeneity (Hh) is simply proportional to the width of the inlet opening (W), even where this is the opening in an orifice plate, i.e., Hh/W = 12.5.