Thermal stress can occur in hot environments where high temperatures cause heat stress to workers. In hot environments, the body responds by trying to remove the excess heat in other words it undergoes heat strain. The excess heat is removed from the body via four processes: when the body comes in contact with a cold surface and loses heat via transfer (conduction), when moving air over the skin takes away heat from the body (convection), through radiation and through evaporation of sweat. After a certain point when the heat intake by the body exceeds the body's ability to dissipate heat, the body's ability in removing excess heat is compromised and the core temperature begins to raise in other words heat stress starts to occur. Extremely hot environments include a high temperature and high humidity that together change the actual heat felt by the worker which can eventually lead to heat stress symptoms. Heat stress can then cause multiple symptoms in the body followed by serious illnesses that may require immediate medical attention.