I've used trapped keyed interlock switches (interlock switch to key located in non-hazardous area) (Allen-Bradley, Omron/STI, and Fortress make them). I've also used explosion-proof Euchner door switches before. Let me know if you'd like more info.
There are a few AIR logic companies that do safety stuff bur the Air is not great. Do you need noticication only or do you need physical locks? If you need indication SICK makes a fiber optic system