What's the difference between these two concepts? When do we use one vs. the other? Any info would be appreciated.
Intrinsically safe means that nothing that normally happens in the circuit and no single abnormal condition will produce a spark or heat sufficient to ignite anything.
Explosion proof means that the containers and conduit between them are designed not to keep explosive gasses or dusts out but to make sure that if (when) the substance ignites inside the container, which is allowed to contain ignition sources, the resulting explosion will not ignite anything outside the container.
It is not even necessary to hold in the pressure of the explosion, just to make sure that the combustion products are too cool to ignite stuff outside once they have gotten out.
