Interior Thermal Environment of a 6-Person Metal-Type Refuge Alternative (RA)

In 2008, the Mine Safety and Health Administration (MSHA) published a final rule on Refuge Alternatives (RAs) for Underground Coal Mines [1]. The rule states that RAs should be “capable of sustaining trapped miners for 96 hours” and that RAs “can also be used to facilitate escape by sustaining trapped miners until they receive communications regarding escape options.” One of the main concerns with the use of RAs is heat and humidity buildup inside of them. The accumulation of heat and humidity could result in miners suffering heat stress or even death. MSHA regulations require that the apparent temperature in an occupied RA must not exceed 95°F. To investigate the thermal issues for occupied RAs, the National Institute for Occupational Safety and Health (NIOSH) conducted several tests on mobile RAs. In this paper, the test setup on a 6-person metal-type RA is described and the test results are presented. The test results show that the average measured air temperature within the RA increased by 9.0°C (16°F) and the relative humidity (RH) approached 91 %RH at the end of the 96-hour test. The test results were also compared to predictions from a thermal simulation model of the tested RA. The model predicted the average air temperature inside the RA at the end of 96 hours to within 0.4°C (0.8°F) of the average measured air temperature. Furthermore, two sets of test data with different heat inputs were used to cross-check the model validity.