Thermal manikin tests were performed on selected protective garments to assess their heat transfer properties during exposure to infrared heat radiation. Comparing a newly developed Infrared (IR) Heat Radiation attenuatuion vest with a standard winter jacket, it could be seen that that the IR Vest provided a thermal comfort benefit above a heat radiation exposure level of 150 Watts while the winter jacket provided a thermal benefit above a 450 Watt heat radiation exposure level. The study identified important temperature cross-over points which define the thermodynamic properties and also characterize the heat radiation attenuation and heat insulation properties of garments. The evaluation method is seen as a new design tool for optimizing garment comfort and safety.