Covers underground tunnels, shafts, chambers and passageways, plus cut-and-cover excavations joined to ongoing underground work and roofed so underground-type conditions arise; Subpart P excavation and trenching and Subpart V underground transmission and distribution lines are excluded. Access and egress: safe routes to every work station, shielded from excavators, haulage units, trains and other mobile plant; openings guarded against unauthorized entry, unused ones tightly covered, bulkheaded or fenced and signed "Keep Out", idle sections barricaded. A check-in/check-out procedure gives the surface an accurate emergency headcount, unless permanent environmental controls work and remaining activity poses no environmental or structural hazard. Workers are instructed in underground hazard recognition and avoidance, covering the ten listed topics where appropriate. Oncoming shifts learn of hazardous occurrences (gas release, cave-ins, floods, fires), and direct communication is kept with other employers whose work affects underground safety. Communications: power-assisted voice links between face, shaft bottom and surface when unaided voice fails; two effective means (at least one voice) in shafts used for access or hoisting; independent power, no single station able to disrupt the rest; tests at each shift's first entry and later as needed; a way for a lone, unobserved worker beyond voice range to summon help. Emergency provisions: prearranged power-assisted hoisting where a shaft serves egress (drum powered both ways, brake applying on power loss) unless normal hoisting survives power failure; NIOSH-approved (42 CFR part 84) self-rescuers immediately available where smoke or gas could trap workers, managed under 1926.103; a designated surface person keeping the count and summoning aid, not overloaded with other tasks; a hand or cap lamp for each worker unless natural or emergency lighting allows escape. Rescue teams: with 25 or more underground at one time, at least two 5-person teams, one on site or within one-half hour travel and one within 2 hours; with fewer than 25, at least one 5-person team on site or within one-half hour. Qualifications are reviewed at least annually; teams practise with SCBA monthly where hazardous flammable or noxious gas quantities are present or anticipated, and know site conditions. Classification: potentially gassy when monitoring shows 10 percent or more of the LEL for longer than 24 hours (measured 12 inches plus or minus 0.25 inch from roof, face, floor or walls) or local history suggests it; gassy at that level for three consecutive days, after an ignition of strata gas, or when connected to a gassy area on a continuous air course carrying the gas. Three consecutive days below 10 percent allow declassification to potentially gassy. Gassy work needs acceptable equipment, MSHA 30 CFR part 36 or equivalent mobile diesels, entrance signs, a smoking ban with collection of lighters and matches, a fire watch per 1926.352(e) during hot work, and a halt to other work in the area (gas control, equipment installation or conversion and surface air-reversal controls excepted) until compliant or declassified. Air monitoring by a competent person: oxygen 19.5 to 22 percent, tested before contaminants; toxics against 1926.55; flammable gas at 5 percent LEL (more ventilation), 10 percent near hot work (stop hot work), 20 percent (withdraw workers above ground and cut power except acceptable pumps and fans); H2S tested at start and midpoint of each shift from 5 ppm until below 5 ppm for 3 consecutive days, a continuous monitor above 10 ppm (employees told when 10 ppm is exceeded) alarming visually and audibly at 20 ppm; continuous gas monitors on rapid excavation machines, plus extra shift testing in gassy and potentially gassy work. Test records (location, date, time, substance, amount) are kept above ground; toxic exposure records per 1910.33, the rest until project completion. Ventilation: at least 200 cfm fresh air per person, 30 feet per minute linear velocity where blasting, drilling or similar dust or gas conditions exist, reversible flow, post-blast exhaust, dust control when drilling, and diesel rules (30 CFR 57.5067, or part 32 for equipment bought on or before July 15, 2019). Later paragraphs: lighting, fire prevention (24-hour diesel limit, no gasoline underground), hot work, ground support with competent person checks each shift, shafts over 5 feet deep, blasting, drilling, haulage checked before each shift, electrical safety, and hoisting: safety devices checked weekly by a competent person, and each hoist assembly load-tested to 100 percent of rated capacity at installation, after structural repairs or safety device operation, and annually, the latest certification record kept until project completion.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.