5. Mistakes to avoid

5.1 Don't ignore human action when it overlaps with automatic action

In certain sectors of activity, where the safety of installations is based on technical MMRs (SISs) which automatically bring installations to safety when threshold parameters (temperature, pressure, gas detection, fire detection, etc.) are exceeded, it is important to identify the MMRs in which the operator intervenes as a redundancy, even if his action is not necessarily valued when estimating accident probabilities. Technical MMRs are not infallible, and it is therefore possible that the operator will one day be obliged to compensate for an equipment failure in order to make the plant safe. Operators must therefore be trained to act in the event of unavailability of "automatic systems".