- high air temperatures
- high surface temperatures
- high humidity
- relatively low air movement
What is heat stress?
Does heat contribute to high accident rates?
How does the human body cope with heat?
The core cannot store an excessive amount of heat without upsetting its delicate thermal balance. Your ability to cope with heat, both at rest and during work, depends upon the stability of your core body temperature. If the core temperature can be stabilized at a high of 100oF (38oC), you will probably be safe.
How does the body release heat?
- Clothing, which can trap heat or slow its rate of release.
- The level of warmth in the surrounding air. Air must be cooler than your skin in order for your body to release the heat.
What are heat disorders, their symptoms, and treatments?
- Heat Rash (also known as prickly heat) is in the form of tiny red blisters in the affected skin area, usually on the neck and upper chest, in the groin, under the breasts, and in elbow creases. This condition is related to the maceration (wasting away) of skin by the continuous presence of unevaporated sweat. Treatment -- Regularly washing and drying the skin are both the prevention and most of the treatment for this rash. Since the rash can develop where clothing is most restrictive, loosen clothing in these sensitive areas. Apply powders to keep the skin dry. Avoid ointments and creams that keep the skin warm and moist -- they may make the condition worse. If blisters form, take care not to burst them; this can allow infection to set in.
- Sunburn damages the skin, sometimes far below the top layer, causing the skin to redden and feel feverish. In more severe cases, fluid-filled blisters form that can become infected. Repeated burns have been linked to forms of skin cancer.
- Treatment -- Apply cold compresses to the sunburned areas. The victim can be immersed in cool water. Stay away from using salves, ointments, or butter that prevents heat from escaping the skin. Some moisturizing lotions help. If blisters form, avoid breaking them; infections can set in to the broken skin.
- Heat fatigue usually indicates a lack of acclimatization; that is, becoming accustomed to the environment. Signs of heat fatigue include impaired performance in jobs that require skill and adeptness in motor activities as well as good judgment and vigilance. In all cases, remove the victim to a cooler area. Treatment -- Since this condition is the first indication of heat stress, removing the victim to a cooler area and allowing time for recovery will normally be enough.
- Heat cramps are muscle pains or spasms -- commonly those in the abdomen, arms, or legs. They can be caused by both too much and too little salt. Cramps often affect people who sweat a lot during strenuous activity. Sweating depletes the body’s salt and moisture; low salt level in muscles cause painful cramps. Treatment -- All activity, once in a cooler area, must stop. Give the victim lightly salted water (1/4 tablespoon of table salt per quart of water) or a beverage that replaces lost electrolytes. If the cramps don’t subside in about one hour or the worker is on a low-sodium diet or has a history of heart problems, seek professional medical attention without delay. If the cramps do let up within an hour, the victim must still remain inactive for a few more hours while drinking proper fluids. Returning to work too quickly can lead to heat exhaustion or heat stroke.
- Heat syncope (heat collapse or heat fainting) occurs when the blood moves from the central organs to vessels in the lower part of the body and to the skin. When blood pools in these extremities, rather than returning to the heart to be pumped to the brain, conditions from light-headedness to fainting occur. Treatment -- Fainting leaves the victim prone and helps the blood that’s pooled in the lower body to circulate back to the brain. As in all cases of fainting, waiting for normal color to return to the victim’s face is a good indicator of recovery. Have the victim drink water (or a clear juice or sports beverage) slowly. After the victim feels like standing up, allow some walking to ensure that a return to work is safe.
- Heat exhaustion (dehydration) or “water-deficiency heat exhaustion” occurs when workers fail to replenish enough fluids and minerals (electrolyte balance) lost during excessive sweating. Symptoms include headache, nausea, vertigo, weakness, thirst, profuse sweating, rapid pulse, dizziness, paleness, muscle cramps, and giddiness. The victim’s skin is clammy and moist; the complexion pale or flushed. Left untreated, heat exhaustion can lead to heat stroke. Treatment -- It is vital that the victim drink lots of lightly salted water (1/4 tablespoon of table salt per quart of water) or a beverage that replaces electrolytes. Plenty of rest away from heat is important. The victim needs treatment from a medical professional as well.
- Heat stroke (sunstroke) is the most serious heat-induced illness. It’s caused by a failure of the body to sweat which results in an accelerating rise in core temperature. Symptoms include confusion, hallucinations, chills, throbbing headache, loss of consciousness, convulsions, slurred speech, and coma. The skin is hot and dry, the pulse is rapid, and blood pressure falls. Body temperature can soar to 106°F (41°C) or more. Heat stroke can cause irreversible damage and is life threatening. Treatment -- This condition can be fatal unless rapid and adequate treatment is obtained! After removing the victim to a cooler area, immediately begin cooling the skin -- for example: loosen clothing, spray with cool water and a fan, or immerse in chilled water coupled with vigorously massaging the skin. Seek treatment from a medical professional without delay while attempting to cool down the victim.
- Engineering Controls
- Administrative Controls and Work Practices
- Personal protective clothing and equipment
Automation and remote controls are effective measures where metabolic heat is a problem, especially in crowded areas. From 50 to 100 percent of the energy set free in blasting shows up in the form of heat. Skillful blasting procedures can reduce the amount of excessive heat.
- Increase workers’ heat tolerance by increasing their physical fitness.
- Provide a work-rest regimen - frequent breaks and reasonably short work periods.
- Pace a task.
- Perform heavy tasks in cooler areas or at cooler times.
- Rotate personnel on hot jobs.
- Provide readily accessible cooler rest areas -- 50 to 60°F (10 to 15°C).
- Provide cool drinking water 50 to 60°F (10 to 15°C) near the workers.
- Encourage all workers to drink a cup of water every 15 to 20 minutes (some authorities recommend “mandatory” water breaks).
- Use extra salt at meals (not for persons on a restricted salt diet by physician’s orders).
- Avoid drinks with caffeine, alcohol, and large amounts of sugar.
- Drink lightly salted water (1 level tablespoon of salt per 15 quarts of water for general use). See treatments for certain disorders for alternate mix of salt and water.
- Caution against drinking extreme amounts of water; generally no more than 12 quarts over a 24-hour period.
- Wear sunblockers and proper protective clothing when working in the sun.
Fabrics that allow some air movement through the weave and those that “wick” wetness away from the body are recommended. If perspiration remains in contact with the skin, it has a better chance of evaporating and cooling the body surface. If perspiration is allowed to run off the body quickly, less evaporation occurs.
- by a single inlet,
- by a distribution tree, or
- by a perforated vest.
- Medical surveillance
Day Percent Exposure
- Worker risk
- The importance of monitoring yourself and coworkers for symptoms
- Personal protective equipment