The amount of heat that stays stored in our bodies as well as the length of time
we remain hot can result in several conditions: Major Heat Stress. Conditions.
Heat Stress Our muscles release about 70% of their energy as heat. Since our bodies work well at a constant inner temperature of 98.6 degrees Fahrenheit, thermoregulation is important. When the environmental temperature is higher than our body temperature, we actually absorb heat. The amount of heat that stays stored in our bodies as well as the length of time we remain hot can result in several conditions:
Major Heat Stress Conditions • Heat cramps • Heat exhaustion • Heat stroke
Minor Heat Stress Conditions • Heat rash • Sunburn • Perspiration and mineral loss
Four Ways to Regulate Extra Heat
Toolbox Talk Your body is affected by heat stress on the job more than you might think. A hot environment with high humidity may overload your body with heat. The result of this extra body heat can range from simple sunburn to very serious disorders like heat stroke. The process of regulating this extra heat is called thermoregulation.
1. Conduction: Use conduction to transfer body heat to objects cooler or warmer than your body. 2. Convection: Use convection to transfer body heat to or from air moving over your skin. 3. Radiation: Use radiation to transfer heat to or from objects not in direct contact with your body. 4. Evaporation: Use evaporation to remove body heat by air or moisture exiting lungs or skin. In radiation, convection and conduction, your blood vessels expand carrying internal body heat to your skin surface for release to the air. In evaporation, perspiration cools on your skin releasing heat to the air.
© Copyright 2009, Jacobs Engineering Group Inc. All rights reserved. xxxx 05/09
Heat Cramps
Heat Exhaustion
Heat Stroke
Heat cramps are severe muscle cramps. They occur when your body’s cellular fluid is depleted through perspiration, cooling or decreased mineral content. Your arms, legs or abdominal muscles can cramp while working or later when relaxing.
Heat exhaustion occurs when the body’s thermoregulation is over-whelmed, but not completely broken down. Since perspiration glands have secreted salts and water onto your skin, fluid loss increases and blood volume drops. You may feel pain from heat cramps, suffer from nausea, headache and eventually collapse.
Heat stroke is the most severe of the heat disorders. Heat stroke is a life-threatening emergency that requires immediate medical attention. Early signs of heat stroke are: • High body temperature, typically above 103 degrees Fahrenheit • Hot, red or flushed skin • Little or no perspiration on skin • Rapid pulse • Difficulty breathing • Weakness • Nausea or vomiting
If you or a co-worker is suffering from heat cramps: • Move into a shaded area • Drink lightly
Heat exhaustion victims must be given immediate medical attention. If you suspect heat exhaustion: • Move victim into shade • Loosen clothing and boots • Circulate air by fanning to cool • Elevate the victim’s legs • If victim is conscious, give lightl salted water • Pour water and ice on victim • Stay with victim until medical help arrives
With heat stroke, the victim’s body temperature must be lowered as quickly as possible. Complete immersion in water or applying ice packs to armpits, wrists or backs of knees may help. Heat stroke is the deadliest of the heat disorders. Call for medical help immediately. Never give fluids to an unconscious person.
Controlling Heat Stress In addition to recognizing the signs of heat stress and knowing first aid measures, you can prevent heat stress disorders: Acclimatization Acclimatization is developing the ability to work in a hot environment by gradually getting yourself used to the conditions. Physical work is necessary for full acclimatization, but should be done with appropriate rest and fluid intake, and at a reasonable pace. Work/Rest Cycles The proper work cycles for reducing the ill effects of heat stress avoid “overdoing it.” It may be that rest means minimal activity instead of stopping work completely. • Try to alternate light and heavy work • When possible, cycle between indoor and outdoor work • Consider rotation of work teams if possible
Fluid Replacement Fluid replacement is the most important way to protect your body’s thermoregulation. You must take in as much fluid as you lose during the day and replace salts your body uses up in cooling. If water and vital electrolytes (salts) are not replaced, dehydration occurs which means there is no perspiration for cooling and results in retained body heat leading to heat stress. Most sports drinks provide electrolyte replacement our bodies need. If you are going to work in the heat, and have no medical reason to avoid salt, add a little to your meals or snacks to help avoid heat stress disorders.
© Copyright 2009, Jacobs Engineering Group Inc. All rights reserved. xxxx 05/09
