The principles of the detection of flammable atmospheres by catalytic devices

Abstract Most instruments used for measuring the explosibility of fuel/air atmospheres use catalytic oxidation as a method of measurement. The detailed mechanism of this method has been examined and equation describing the output from these devices have been derived. The output V(LEL) at the lower explosive limit of a fuel has the general form V (LEL) =K D 12 δH[LEL], where D12, ΔH, and [LEL] are respectively the diffusion coefficient, heat of oxidation, and the lower explosive limit of the fuel in air, and K is a constant. Calculations have been made which enable the responses to explosive gas/air mixtures to be predicted and correction factors to be derived for practical devices. A new method for the measurement of explosiveness is discussed based on the empirical correlation between the heat of oxidation of the fuel and its lower explosive limit.