Safety - Heat Stress - Recreational Activities, Southwestern Region, USDA Forest Service

Recreational Activities

SAFETY: Heat Stress

Safety Tips | Heat Stress | Exposure/Hypothermia

Heat Stress occurs when humidity, air temperature, radiant heat, and too little air movement combine with heavy work and clothing to raise the body temperature beyond safe limits. Sweat, as it evaporates, is the body's main line of defense against heat—as sweat evaporates it cools the body. In high humidity, sweating becomes more intense but doesn't evaporate, so no heat is lost. When water lost through sweating is not replaced, the body's heat control breaks down and body temperature climbs dangerously, subjecting the body to heat stress.

Preventing Heat Stress

Maintaining a high level of physical fitness is one of the best ways to protect yourself. The physically fit person has a well-developed circulatory capacity, as well as increased blood volume—important in regulating body temperature.

The person acclimated to the heat runs less risk of heat stress. The body adjusts to hot work in 4 to 8 days by:

Increasing sweat production.
Improving blood distribution.
Decreasing skin and body temperature.
Decreasing heart rate (beats per minute for the same job may drop from 180 to 150).

Acclimatization may be hastened by taking 250 milligrams of vitamin C daily. About 1-1 1/2 hours of work a day in the heat is enough to acclimatize to a specific combination of work and heat. It provides partial acclimatization to more severe conditions. Adjust to hot weather activity gradually. Set a sensible pace, take frequent breaks, replace fluids, and don't expect full production the first few days. Acclimatization persists for several weeks, but a tough weekend (fatigue, alcohol) leads to some loss.

Recognizing and Treating Heat Stress Disorders
Heat Stress Disorder	Cause	Symptoms	Treatment
Heat Cramps	Failure to replace salt lost in sweating.	Painful muscle cramps.	Drink lightly salted water or lemonade; tomato juice, or "athletic" drinks; stretch cramped muscles.
Heat exhaustion	Failure to replace water and salt lost in sweating.	Weakness, unstable gait, or extreme fatigue; wet, clammy skin; headache, nausea, collapse	Rest in shade and drink lightly salted fluids.
Dehydration exhaustion	Failure to replace water losses over several days	Weight loss and excessive fatigue.	Drink fluids and rest body weight and water losses are restored.
Heat stroke	Total collapse of temperature regulating mechanisms.	Hot skin; high body temperature (106°F or higher); mental confusion, delirium, loss of consciousness, convulsions.	Rapidly cool victim immediately, either by immersing in cold water or soaking clothes in cold water and fanning vigorously to promote evaporative cooling. Continue until temperature drops below 102°F. Treat for shock if necessary once temperature is lowered. Heat stroke is a medical emergency. Send for medical help and begin treatment at once. Brain damage and death result if treatment is delayed.