5. Components of ignition probability

5.1 Presence and efficiency

In simplified terms, for each ignition source, the probability of ignition depends on two components:

• the probability that the source is present at the same time as the flammable cloud; this parameter is often referred to in the literature as the "presence factor";

• the probability that the source will be of sufficient energy to ignite the cloud over a given time interval; this parameter is often referred to in the literature as the "strength factor".

By way of example, if we consider a low-energy torch whose utilization rate is 20% (i.e. the torch operates 20% of the time), and if we assume that for such a source the probability of the cloud...