30 CFR §56/57.4101 Warning signs.
Readily visible signs prohibiting smoking and open flames shall be posted where a fire or explosion hazard exists.
There is no MSHA policy for this standard.
30 CFR §77.1102 Warning
signs; smoking and open flame.
Signs warning against smoking and open flames shall be posted so they can be readily seen in areas or places where fire or explosion hazards exist.
30 CFR § 75.1702 Smoking;
MSHA policy can be found here: 75.1702
These standards require that readily visible signs prohibiting smoking or open flames be posted in areas where a fire or explosion hazard exists (metal and nonmetal and coal surface and metal and nonmetal underground).
Other relevant MSHA standards:
75.1702-1 Smoking programs
75.1107-17 Incorporation by reference; availability of publications
77.1102 Warning signs; smoking and open flame
77.1103 Flammable liquids; storage
77.1104 Accumulations of combustible materials
• Are warning signs posted near storage and dispensing areas for flammable or combustible liquids?
• Are warning signs posted near storage and dispensing areas for grease? Although greases may be more difficult to ignite than flammable liquids, once ignited they burn intensely and are difficult to extinguish.
• Are warning signs posted near storage areas for flammable gases?
• Are warning signs posted near areas where flammable or combustible liquids or flammable gases are used or transported in a manner that could create a fire hazard?
• Are signs posted in vehicles transporting flammable liquids, for persons who smoke, that such transport could create a fire or explosion hazard?
• Are the signs readily visible to all persons in the area and adequate to warn persons of the hazardous area?
• Do warning signs inform a "reasonable person" that smoking or the use of open flames should not occur in the area?