The participants will undergo an examination day in which they will complete VO2max test to evaluate their aerobic fitness. Afterwards they'll undergo 3 heat tolerance test (HTT) days: without CB protective clothing, with CB protective clothing, and with work clothes. During the tests, a "Lifebeam" sensor will be attached to their skin.

The "lifebeam" sensor will be attached to the participant's skin during the HTT.

The test is performed in a climatic chamber at a temperature of 40oC and 40% relative humidity. During the test, the subject walks on a treadmill at a speed of 5 km/hr at a 2% grade for 2h. Body core temperature and heart rate are continuously monitored, and sweat rate is computed from body weight prior to and after the test, corrected for fluid intake. Heat intolerance is determined when body core temperature elevates above 38.5oC, when heart rate elevates above 150 bpm, or when either does not tend to reach a plateau.

Volunteer's oxygen consumption (VO2) will be monitored continuously with a metabolic chart (ZAN), while running for 10 min on a treadmill under comfortable environmental conditions.

The volunteers will undergo heat tolerance test. Their skin temperature will be measured by skin thermistors and will be monitored continuously and viewed by the attending medical staff. Automatically all data will be recorded by the monitoring Biopac system.