At what surface temperature does OSHA require a “Hot” sign?

OSHA does not specifically indicate a temperature at which surfaces must be marked with a sign warning of a hot surface hazard. However, 1910.252(b)(4)(vii), says, “After welding operations are completed, the welder shall mark the hot metal or provide some other means of warning other workers.”

Also, 1910.145 requires that signs or symbols be posted near hazards likely to cause an accident, injury, or property damage, unless other effective means like proper training are taken. Therefore, when hot surface hazards are of a nature such that failure to designate them may lead to accidental injury to workers or the public, or both, or to property damage, signs or other effective means, like proper training, are required.