Zone 2 equipment is suitable for lower-risk hazardous areas at a greater distance from the explosion risk or the point at which combustible vapours are being released.

This is the hazardous area equipment that bridges the gap between the zones of highest risk – where Zone 0 or Zone 1 equipment is needed – and the surrounding areas where the threat level drops low enough to be negligible.

However, it is important to correctly calculate the boundary of where Zone 2 equipment is sufficient to overcome the threat.

New research published in the Journal of Health and Safety at Work looks at the optimisation of the calculation of hazardous area boundaries using a risk-based approach.

The authors write: “Leakage from process equipment and the entrance of flammable fluids to the surrounding atmosphere may cause a flammable gas cloud.

“The coincidence of a flammable gas cloud with an ignition source could make a flash fire or vapour cloud explosion that causes injury and fatality.”

By factoring in multiple sources of vapour leaks and the drift effect of downwind locations from these points, they say Zone 2 hazardous areas can be calculated much more accurately.

As always, the different zones form a hierarchy – so Zone 0 equipment can be used in any location, Zone 1 equipment is suitable for both zones 1 and 2, and Zone 2 equipment should be used where there is a high degree of confidence that the threat level is relatively low or temporary.