4. Our advice

4.1 In the absence of a "robust" demonstration, assume a probability of total ignition equal to 1 as soon as the flammable cloud leaves the site boundaries.

On industrial sites, preventive measures (organizational and/or design) reduce the probability of ignition. As a result, "small" leaks confined to the site generally have little chance of igniting. On the other hand, if a flammable cloud leaves the site boundaries, the probability of ignition may be higher or lower, depending on the area affected (urbanized or non-urbanized area, road, etc.). For this type of release, we recommend a total probability of ignition equal to 1 (all the more so if the MMRs used to limit the duration of the release are deemed to have failed).