We are having a contractor install an HMI touch screen in our coal fired power plant. It will be installed near some coal conveyors. My understanding is that this area is a Class II, Division 1 location because even with our dust collector system running coal dust accumulates everywhere on that deck. As far as we know an area clasification study has not bin done here. Some people here are saying it is ok to buy a NEMA 4 enclosure, cutt a hole into the cover for the HMI and seal it to the enclosure door and presurize the enclosure with plant air. This home made enclosure dosen't seen right to me. I beleve the enclosure needs to be manufactured for this area. Any thoughts or an old thread someone can direct me to that might help me end up with the proper installation?