Radiation - the transfer of heat to the body through air from a hot source, for example, a furnace, an oven, or the sun. This is an important factor as, again, heat is lost from the body only if the surrounding air is cooler than the body. Evaporation - evaporation of sweat from the skin cools the body. At very high humidity however, sweat does not evaporate as quickly. High air speed and low humidity increases evaporation.
Dehydration is a common problem from working in heat.
As shown in Table I , it is caused by failure to replace salt and water lost from sweating. Although sweating is necessary to help cool the body, the fluid and salt loss must be replaced. On average, one to two cups of water per hour is required to replace fluid lost from heavy sweating. Cool but not cold, fluids should be provided, in a location convenient to workers. Because the feeling of thirst may not be enough to ensure adequate fluid intake, workers in hot environments should be encouraged to drink at least one cup per hour.