Icheme Symposium Series No. 144 the Sensitivity of Risk Assessment of Flash Fire Events to Modelling Assumptions

Based on reviews of modelling techniques and data from flash fire field trials, models for the prediction of the burn area of a flammable cloud (in terms of fraction of mean LFL of the cloud), flame speed through the cloud and heat transfer from the flash fire have been produced. The validity of the typical assumptions used in the modelling of flash fires has been tested through comparison against these models and a set of revised assumptions is provided relating to the likelihood of fatality of people caught within a flash fire and the mitigating effects of shelter and escape from the cloud. A sensitivity analysis is performed in order to identify which assumptions or aspects of flash fire modelling are the most critical in terms of off-site risk. The analysis suggests that risk assessments are most sensitive to the definition of burn area of the cloud, and therefore also to dispersion modelling, and to the proportion of people within shelter who are fatalities as a result of secondary fires.