A second can change your entire life. To have 1 additional second in a risky situation can make a huge difference! No matter if you are a soldier, fire fighter, racecar driver or industrial worker, heat stress is a global issue and still fatality reason number one for fire fighters. In the recent years a lot of physiological studies have been carried out, mainly by military forces an institutes. The purpose of this studies was to evaluate the thermo-physiological properties of protective clothing and its influence to metabolic exchange. Human body is a bad machine. It is quite inefficient! During physical activity only 25% of energy is turned into movement the rest is body heat. For this reason, physical strain leads automatically to heat stress. This presentation is addressing the performance of different FR materials, in a scientific study, with respect to physiological performance