7. Frequently asked questions

Is the estimation of ignition probabilities mandatory in hazard studies?

The Étude De Dangers does not require the quantification of ignition probabilities. If ignition probabilities are not quantified, it must be conservatively assumed that all releases of flammable products are ignited. In other words, this amounts to assuming an ignition probability equal to 1. This assumption may prove relatively conservative in the case of small leaks which form a flammable cloud that only extends into ATEX-classified zones. In these zones, preventive measures are taken to limit the probability of ignition (ATEX equipment, special work instructions, etc.). In the case of "major" leaks with effects outside site boundaries, a default probability of ignition equal to 1 may seem reasonable if the cloud drifts towards areas with a high density of ignition sources (zones of activity,...