Fire Safety Science Digital Archive

Measurements of the composition of combustion gases, withdrawn from different points of a vent at the top of one face of a 0.9 m cubical compartment, have shown that the gases withdrawn from the centre of the vent and 2 cm below the ceiling of the compartment have about the same composition as the average composition of all the evolved combustion gases for a fire disposed centrally on the floor of the compartment. Comparison with calculated rates of evolution of combustion gases from data obtained from the above sampling position, by mass balance and heat balance methods, has shown that the rate of flow may be estimated with good accuracy by the use of a simplified form of the equation proposed by Kawagoe, provided that a discharge coefficient of 0.9 is incorporated in the equation. Errors in measurement introduced by neglect of water vapour formed during combustion are small.