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.
