Federal regulations require the installation of refuge alternatives (RAs) in underground coal mines. Mobile RAs have a limited ability to dissipate heat, and heat buildup can lead to a life-threatening condition as the RA internal air temperature and relative humidity increase. The U.S. National Institute for Occupational Safety and Health (NIOSH) performed heat testing on a 10-person tent-type training RA and contracted ThermoAnalytics Inc. to develop a validated thermal simulation model of the tested RA. The model was used to examine the effects of the constant mine strata temperature assumption, initial mine air temperature, initial mine strata surface temperature (MSST), initial mine strata temperature at depth (MSTD) and mine strata thermal behavior on RA internal air temperature using 117 W (400 Btu/h) of sensible heat input per simulated miner. For the studied RA, when the mine strata temperature was treated as a constant, the final predicted RA internal air temperature was 7.1 °C (12.8 °F) lower than it was when the mine strata thermal behavior was included in the model. A 5.6 °C (10 °F) increase in the initial MSST resulted in a 3.9 °C (7.1 °F) increase in the final RA internal air temperature, whereas a 5.6 °C (10 °F) increase in the initial MSTD yielded a 1.4 °C (2.5 °F) increase in the final RA internal air temperature. The results indicate that mine strata temperature increases and mine strata initial temperatures must be accounted for in the physical testing or thermal simulations of RAs.