Application of thermochemical energy hazard criteria to the prediction of lower flammability limits of hydrocarbons in air

The energy hazard criteria of ASTM program CHETAH have been tested as criteria of flammability of gaseous mixtures containing an hydrocarbon vapour and air as oxidiser, at lean concentrations. A method for calculating the lower flammability limits in air, at atmospheric pressure and ambient temperature, is proposed as a result of a statistical study, which involved 67 combustible compounds. CHETAH's fourth energy hazard criterion was found to be the most reliable flammability criterion. The method is predictive since all the input data may be obtained with very good accuracy using a group contribution method. It is reliable, predicted limits being more frequently underevaluated, by 0.11 mo1% on average, than overevaluated. The method is also precise, with a standard deviation of the estimates of 0.14 mol%. It is easily applicable to fuel mixtures and gives the same results as Le Chatelier's law.