I've asked the question before about 501(E)(1) & 501(E)(3) and if seals are required for cables terminated in non-explosionproof enclosures in a Class 1 Division 2 area and if they transition from Class 1 Division 2 to a Non Classified area such as a MCC room. The response was no seal required unless the cable is attached to process equipment or devices. My follow up question is more along the lines of an explanation why that is. I'm trying to understand is it because the cable core is tight enough so that it can't pass gas or vapor unless it is pressurized? 1500 pascals or .2175566 pounds per square inch isn't much pressure.