I have dealings with IRI (Industrial Risk Insurers) when installing ovens and heaters in the auto plants. Each one of these pieces of equipment must meet IRI's approval before installing, and one of the things that they deal with is explosion relief for enclosures, and their standard is: 1 Square Foot of relief for every 15 Cubic Feet of enclosure as a minimum. Hopefully this helps, but then again I am dealing with gas and the products of combustion.
