Weather the Elements

Weather the Extremes

A Guide to Managing Heat Stress

It’s not your imagination. It IS hotter outside. In fact, summer temperatures over the last decade have been the hottest on record.
Since 1983, U.S. heat waves have caused more deaths than hurricanes and floods combined.

The Hazards of Heat Stress

Heat stress occurs when the body cannot get rid of excess heat. The body's core temperature rises, and the heart rate increases. As the body continues to store heat, the person begins to lose concentration and has difficulty focusing on a task. He or she may become irritable or sick, and often loses the desire to drink. The next stage is fainting and possibly death if the person is not cooled down.

Factors that contribute to heat stress are high temperatures, radiant heat exposure, high humidity, direct physical contact with hot objects, and strenuous physical activities.

Effect Symptoms Cause Treatment Prevention
Heat Rash (aka “prickly heat”) Small, itchy blister-like bumps; prickling sensation when exposed to heat Excessive sweating plugs sweat glands, increasing sweat retention deep in the skin, reducing the body’s ability to cool itself Move to a cooler, less humid work environment. Apply mild drying lotions. Keep skin clean to prevent infections. Wear work clothes that promote evaporative cooling. Sleep in a cool area to dry the skin.
Heat Cramps Painful muscle spasms during work activities (arms, legs or abdominal) Loss of body salt due to sweat. Water intake dilutes electrolytes, and enters the muscles, causing spasms. Drink salted liquids Consume more salt with meals and drink salted drinking water.
Heat Exhaustion Fatigue, nausea, headache, giddiness, clammy moist skin, pale complexion. May faint upon standing with rapid pulse and low blood pressure. Sustained exertion in heat, lack of acclimatization, failure to replace water and/or salt lost in sweat Move person to cool shaded area to rest—Do not leave them alone. Loosen or remove heavy clothing. Have person drink cool water (a small cup every 15 minutes) if possible. Fan and cool their skin with a wet cloth. Acclimatize workers using a breaking-in schedule for 1 or 2 weeks. Supplement dietary salt only during acclimatization. Drink water frequently during the workday.
Heat Stroke—Medical Emergency Hot dry skin, red, mottled or cyanotic. High and rising temperature. Mental confusion, loss of consciousness. Fatal if treatment is delayed. Sustained exertion in heat by acclimatized workers. Lack of physical fitness and obesity. Recent alcohol consumption. Dehydration. Immediate and rapid cooling by immersion in chilled water w/ massage or wrap in wet sheet with vigorous fanning using cool dry air. Medical screenings of workers. Selection based on health and physical fitness. Acclimatization for 8-14 days. Monitoring workers during sustained work in severe heat.

Ways to Protect Your Workers from Heat Stress

  • Learn the signs and symptoms of heat-induced illnesses and what to do to help the worker.
  • Train the workforce about heat-induced illnesses.
  • Perform the heaviest work in the coolest part of the day.
  • Slowly build up tolerance to the heat and the work activity (usually takes up to two weeks).
  • Use the buddy system (work in pairs).
  • Drink plenty of cool water (one small cup every 15–20 minutes).
  • Wear light, loose fitting, breathable (like cotton) clothing.
  • Take frequent short breaks in cool shaded areas, allowing your body to cool down.
  • Avoid eating large meals before working in hot environments.
  • Avoid caffeine and alcoholic beverages. They make the body lose water and increase the risk for heat illnesses.

Workers Are at Increased Risk When...

  • They take certain medication. Check with a doctor, nurse or pharmacy and ask if any medications affect you when working in hot environments.
  • They have had a heat-induced illness in the past.
  • They wear personal protective equipment (like respirators or suits).


Preventing Heat Stress Using the Hierarchy of Controls

The Occupational Health and Safety Act mandates that employers provide their workers a place of employment that is free from recognized hazards likely to cause death or serious physical harm. Below you’ll find practices and techniques that can eliminate the dangers of heat stress from your work environment.

Heat stress prevention techniques fall into three general categories, based on their effectiveness. The first category is engineering controls that limit the environmental heat load and improve the rate of heat elimination from the body. The second category involves changes to work practices and administrative controls that reduce workplace heat stress. The third category includes training and personal protective equipment (PPE) to limit the heat stress risk.

Engineering controls modify the rate of heat exchange between workers and their environment. Air temperature and velocity are the main factors that affect heat lost or gained in the body. Heat loss occurs when the ambient air temperature is lower than skin temperature (approximately 95°F). Under these conditions, increasing air velocity with fans can increase the rate of heat loss. If the ambient air temperature is greater than 95°F, increasing ambient air velocity will cause the body to gain heat.

To reduce the effects of radiative heat, place a reflective screen between the radiant heat source and the worker(s). The type of reflective screen can vary in complexity, from insulated furnace jackets to reflective metal shields or reflective clothing like firefighters wear. Covering the body in normal clothing can also provide some protection from radiant heat sources.

Engineering Control Recommendations:

  • Increase air velocity (if ambient air temp is 95°F or below).
  • Use reflective or heat-absorbing shielding or barriers.
  • Reduce steam leaks, wet floors, or humidity.

Reduce the chance of heat stress through work practices that control the rate of body heat generation. This can be achieved by scheduling hot or strenuous work during cooler parts of the day. Workers should also have an opportunity acclimatize to hot conditions.

Frequent rest breaks help limit core heat buildup and allows the body time to dissipate excess heat. Sometimes it may be necessary to use a larger workforce for especially hot jobs to ensure the work-rest schedule can be maintained.

Administrative Practice Recommendations:

  • Limit time in the heat and/or increase recovery time spent in cool environment.
  • Use special tools (i.e. tools intended to reduce manual strain).
  • Increase the number of workers per task.
  • Implement a buddy system to observe signs of heat intolerance.
  • Provide adequate amounts of cool, portable water near the work area and encourage workers to drink frequently.
  • Implement a heat alert program whenever the forecast includes heat wave conditions.
  • Institute a heat acclimatization plan and increase physical fitness.



Training and PPE

Worker training is a critical aspect of a heat stress prevention program. Program objectives should include:

  1. Training supervisors and workers to watch for the signs and symptoms of heat strain and how to treat them.
  2. Training supervisors the importance of allowing workers to acclimatize to hot conditions and self-pace their work rate during high heat exposure.
  3. Understanding the importance of regularly drinking water regardless of thirst and making water readily available for workers in the heat.

To reduce heat stress incidents, conduct medical screenings for workers exposed to hot work environments. This will help identify employees with limited heat coping ability due to existing health problems such as heart disease. Other measures such as reflective clothing or personal ice vests can limit heat buildup and extend the time a person can work in a hot environment without undue risk of heat stress.

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