(1) Acclimatization. The body's temporary adaptation to work in heat that occurs as a person is exposed to it over a period of seven to 14 days depending on the amount of recent work in the heat and individual factors. Acclimatization can be lost after seven consecutive days away from working in the heat.

(2) Buddy system. A system where individuals are paired or teamed up into work groups so each employee can be observed by at least one other member of the group to monitor and report signs and symptoms of heat-related illness.

(3) Drinking water. Potable water that is suitable to drink and suitably cool in temperature. Other acceptable beverages include drinking water packaged as a consumer product, and electrolyte-replenishing beverages (i.e., sports drinks) that do not contain high amounts of sugar, caffeine, or both such as energy drinks.

(4) Engineering controls. The use of devices to reduce exposure and aid cooling, not including wearable items. Examples of engineering controls include fans, misting stations, air-conditioning, etc.

(5) Heat-related illness. A medical condition resulting from the body's inability to cope with a particular heat load, and includes, but is not limited to, heat cramps, heat rash, heat exhaustion, fainting, and heat stroke.

(6) Outdoor environment. An environment where work activities are conducted outside. Work environments such as inside vehicle cabs, sheds, and tents or other structures may be considered an outdoor environment if the environmental factors affecting temperature are not managed by engineering controls.

(7) Risk factors for heat-related illness. Conditions that increase susceptibility for heat-related illness including:

(a) Environmental factors such as air temperature, relative humidity, air movement, radiant heat from the sun and other sources, conductive heat sources such as the ground;

(b) Workload (light, moderate, or heavy) and work duration;

(c) Personal protective equipment and clothing worn by employees; and

(d) Personal factors such as age, medications, physical fitness, and pregnancy.

(8) Shade. A blockage of direct sunlight. Shade may be provided by any natural or artificial means that does not expose employees to unsafe or unhealthy conditions and that does not deter or discourage access or use. One indicator that blockage is sufficient is when objects do not cast a shadow in the area of blocked sunlight. Shade is not adequate when heat in the area of shade defeats the purpose of shade, which is to allow the body to cool. For example, a car sitting in the sun does not provide acceptable shade to a person sitting in it, unless the car is running with air-conditioning.

(9) Vapor barrier clothing. Clothing that significantly inhibits or completely prevents sweat produced by the body from evaporating into the outside air. Such clothing includes encapsulating suits, various forms of chemical resistant suits used for PPE, and other forms of nonbreathable clothing.