We had an analysis of our equipment done at our plant (welding receptacles, MCC's, etc) and the report states for several pieces of equipment that the enclosures need to be replaced with NEMA 9 enclosures due them being in Class II Division II areas. I cannot find anything definitive that states that NEMA 9 enclosures are required for these areas. The areas are indeed Class II Div II areas, as there is a lot of coal dust present, but is there any specific reference to what the enclosure requirements are for these areas? It is very confusing with terms such as "dust-tight" being used, but not a clear definition of what exactly that means. I can see that NEMA 9 would be sufficient, but is it overkill? I don't want to make any unnecessary changes if it is not required. Very much appreciate the insight as always.