The federal OSHA standard(s) are not very helpful when it comes to guidance on guarding hot surfaces and this causes many debates during audits, HAZ assessments, and Pre-Start Up Safety Reviews (PSSR). We probably are all aware of the seven (7) feet rule for guarding “fan blades”…
1910.212(a)(5) Exposure of blades. When the periphery of the blades of a fan is less than seven (7) feet above the floor or working level, the blades shall be guarded. The guard shall have openings no larger than one-half ( 1⁄2 ) inch.
The idea is that if the hazard is 7′ or further overhead, we are protected by “distance/proximity” to the hazard. OSHA makes no mention of this concept in their General Guarding standard in relation to hot surfaces, however, there is an OSHA State Plan that provides us with some reasonable requirements for guarding hot surfaces.
NOTE: OSHA does have a 1998 LOI where they discuss their expectations for guarding hot surfaces, but as the LOI points out there really is no guidance in any of those standards for hot surfaces. Here is a GDC citation for unguarded hot surfaces.