Federal regulations require refuge alternatives (RAs) in United States underground coal mines. If the thermal environment in an RA becomes severe, trapped miners could experience heat exhaustion or heat stroke, which is deadly. Regulations for underground coal mine RAs mandate an apparent temperature (AT) limit of 35°C (95°F). The National Institute for Occupational Safety and Health (NIOSH) conducted in-mine temperature/humidity tests to evaluate three RA heat mitigation devices: a conditioned borehole air supply (BAS), a battery-powered air conditioner (BPAC), and a cryogenic air supply (CAS). The BAS limited the AT in a 60-person built-in-place (BIP) RA to 25°C (77°F) when the outside air temperature was 10°C–23.9°C (50°F–75°F) and with relative humidity from 50%–95%. During tests with a 29.4°C (85°F) mine air temperature, the BPAC and CAS kept the AT below (95°F). The CAS was also shown to allow for 12 miners in a 29.4°C (85°F), 30-person BIP RA. This information can be used by RA manufacturers and mines to ensure occupied RAs can meet the 35°C (95°F) AT limit.

The Onaping Depth Project is a nickel/copper underground mine project currently in execution by Glencore's Sudbury Integrated Nickel Operations. The Onaping Depth orebodies will be accessed via the existing Craig Mine workings after completion of sinking a winze from 1,200 to 2,640m below surface. Due to the final depth of the workplace, a 16 MW(R) underground refrigeration plant will be operated at a depth of 1,915m below surface to provide conditioned air to the workplace throughout the project development and life of mine production phases. This paper will provide an update on the design, construction and commissioning of the underground refrigeration plant, including lessons learned in the contracting and construction methodologies.

Federal regulations require refuge alternatives (RAs) in United States underground coal mines. The thermal environment of RAs is a concern because, if the thermal environment in an RA becomes severe, trapped miners could experience heat exhaustion or heat stroke, which is deadly. To prevent exposing RA occupants to heat stress, regulations for underground coal mine RAs mandate an apparent temperature (AT) limit of 35°C (95°F). To examine occupancy derating to meet the AT limit, NIOSH conducted RA thermal simulations with actual mine strata and temperature data using validated thermal simulation models. NIOSH examined occupancy derating for a portable 23-person tent-type RA and a portable 6-person rigid RA across a range of initial temperatures for the mine strata of its Experimental Mine. For these RAs, occupancy derating was necessary for mine temperatures as low as 60°F. NIOSH also examined occupancy derating for each of the RAs for five mines across the United States using measured worst-case temperatures and the mine strata of each mine. The results showed occupancy derating would be necessary for the mines with relatively warm initial temperatures. RA manufacturers and mines can use this information to ensure RAs do not exceed the AT limit.