Rockwell aren't designing, building or certifying the panel, and neither am I. A company that specialises in building and certifying hazardous area equipment is. My part in this is simply to make sure that when I put the program in the PLC, it stays there. All of the design decisions regarding this panel (beyond which PLC I ask them to put in it) are being made by a company that are world leaders in designing controls for hazardous areas. I'm confident they know what they're doing.