Anyone who works at a business that has a formal hotwork program can recite the distance at which all fire safety requirements must be in place… 35′. But this 35′ is a “magical number” to many who use it on a daily basis. Don’t believe the number is “magical”? Just go out and ask your permit approvers or your welders why the “35′ rule” is not the “25′ rule” or the “45′ rule”. Before reading this article, could you explain to your management and workers why 1910.252(a), NFPA 51B, and FM Global’s Data Sheet 10-3 uses 35′ for the fire safe area? Here is the explanation of the 35′ rule and some other helpful Hotwork safety information.