employee heat stress

When it comes to working in a hot environment, there’s no such thing as too much preparation. Excessive heat and sun exposure can pose a significant risk to employees, especially those working outside in the direct sun, like roofers and road workers.

According to the Occupational Health and Safety Administration (OHSA), heat stress in the workplace causes thousands of illnesses and dozens of fatalities each year. Fortunately, there are ways for employers and employees alike to help prevent these injuries from happening.

Today, we’ll explore the risk of heat stress and the several measures that you can take as an employer to keep your crew safe.

What is Heat Stress?

Heat stress is a health hazard that occurs when a person is exposed to high temperatures and humidity. It can occur indoors (mills, foundries, interior renovation, etc.) or outdoors (roofing, home-building, road work, etc.), and protective clothing can further exacerbate the problem. When workers perform strenuous work in a sweltering environment, they build up body heat, causing their core temperature to rise.

To eliminate this excess body heat and reduce internal temperatures, our body uses two cooling mechanisms:

  • Our heart rate increases to move blood–and heat–from the heart, lungs and other vital organs to the skin.
  • Sweating increases to help cool the body. In fact, sweating is the most important way the body gets rid of excess heat.

When too much sweat is lost through heavy labor or working under hot, humid conditions, the body lacks enough water to cool itself down, causing dehydration. Not long after, our core temperatures rise above 38°C and a series of heat-related illnesses, or heat stress disorders begin to develop.

Common Heat Stress Disorders Prevalent in the Workplace

Each year in North America an estimated 220 workers die from occupational heat stress. What’s more, scientists predict the worst is yet to come. A study released by Toronto Public Health and Environment Canada anticipates heat-related deaths to double by 2050 and triple by 2080 as a result of global warming.

Heat stress disorders can range from minor discomfort to life-threatening ailments, and include the following:

Heat Rash

Heat rash, also known as prickly heat, is the most common heat stress disorder in work environments. Appearing as red blotches on the skin, heat rash results in extreme itchiness and/or a prickling sensation in areas damp with sweat. Common treatments for heat rash include staying in a cool environment, taking a cool shower, and keeping dry. In most cases, the rash should disappear on its own within a few days once the individual is no longer subjected to heat.

Heat Cramps

Heat cramps are sharp muscle spasms that often occur in workers who sweat profusely in the heat, drink plenty of water, but do not adequately replenish the body’s loss of salt.

Heat cramps most frequently occur in large muscles like the back, legs and arms. Workers may begin to notice cramping while still on site or later on after they’ve clocked out for the day.

To treat heat cramps, it’s best to gently stretch and massage the affected muscles and replenish the body’s loss of salt by drinking beverages with electrolytes. If heat cramps are severe, it’s important to seek medical attention right away.

Heat Exhaustion

Heat exhaustion is a mild form of heat illness that occurs when the body overheats and loses large amounts of water and salt usually through excessive sweating from continuous work in high temperatures.

Signs of heat exhaustion may include:

  • Extreme weakness
  • Dizziness
  • Nausea and vomiting
  • Muscle cramps
  • Breathlessness
  • Headache
  • Feeling faint or actually fainting
  • Numbness of the hands or feet

An individual showing signs of heat exhaustion at work needs to be cooled down and given fluids immediately. Here’s what to do if you suspect an employee is experiencing heat exhaustion:

  • Move them to a cool place
  • Remove all unnecessary clothing (jackets, socks, etc.)
  • Get them to drink a sports or rehydration drink or cool water
  • Cool their skin­. Spray or sponge them with cool water and fan them. Grab cold packs wrap them in cloth and put them under their armpits or on their neck.

Employees suffering from heat exhaustion should begin to cool down and feel better within 30 minutes.

Heat Stroke

The most serious heat stress disorder, heat stroke occurs when a person’s own body can no longer cool itself down. Sweating fails to keep the body temperature within a normal range and as a result, the body’s core temperature rises to critical levels.

Unlike the above disorders, heat stroke requires immediate medical attention. If not treated instantly, it can result in permanent damage to vital organs such as the heart, brain, and kidneys.

The primary signs and symptoms of heat stroke include:

  • Mental confusion
  • Lack of sweating
  • Irrational behavior
  • Hot, dry skin that is red or spotted
  • Loss of consciousness
  • Abnormally high body temperature (for example, 41°C)
  • Convulsions

If you suspect an employee is suffering from heat stroke, call 911 immediately and stay with the worker until emergency medical services arrive. While waiting, complete the following steps:

  • Move the worker to a shaded, cool area and remove their outer clothing
  • Cool the worker quickly with one of the following: a cool water or ice bath, wetting the skin, placing cold wet washcloths on the skin, or soaking clothing with cool water
  • Circulate the air around the worker to speed up cooling
  • Place cold wet washcloths or ice on the worker’s head, neck, armpits, and groin; or soak their clothing with cool water

Heat Stress Prevention in the Workplace

You can’t control the weather. But you can control your company’s approach to working in the heat. Managing heat stress in the workplace allows you to prevent and treat symptoms while they are still mild. Early prevention includes adopting a culmination of engineering, training, and work practice controls as well as establishing a heat stress policy.

Engineering Controls

When it comes to engineering controls it’s all about prevention. When there’s no other option but to work during the hottest parts of the day, ensure workers are taking regular breaks and staying hydrated under the covers of shelters like canopies, umbrellas, and other temporary structures. These shelters should include ample shade, plenty of water, and a place for workers to recharge. If your work environment is indoors and you’re able to reduce the temperature and humidity with AC, even better!

Educate and Train

When it comes to your crews’ health and safety, education and training are vital.

The National Institute of Occupational Safety and Health (NIOSH) states heat stress training should cover the following:

  • Knowledge of heat stress hazards
  • Recognition of risk factors, danger signs and symptoms
  • Awareness of first-aid procedures for, and potential health effects of heat stroke and other heat-related illnesses
  • Employee responsibilities in avoiding heat stress
  • Dangers of using alcohol and/or drugs (including prescription drugs) in hot work environments.

Appropriate Work Procedures

Teamwork makes the dream work. The risks of working in hot environments can be significantly reduced if management and labors work together to manage heat stress.

Here are some of the ways these parties can come together to ensure optimal health and safety on all fronts:


  • Provide workers frequent breaks in a cool area away from heat
  • Increase air circulation by using fans where possible. This encourages body cooling through the evaporation of sweat
  • Provide unlimited amounts of cool drinking water and ensure that it is always conveniently located
  • Offer workers sufficient time to become acclimatized. A properly designed and applied acclimatization program decreases the risk of heat-related illnesses by gradually exposing employees to work in a hot environment. NIOSH recommends that for workers who have had previous experience working in hot environments, the regimen should be:
    • 50% exposure on day one
    • 60% exposure on day two
    • 80% exposure on day three
    • 100% exposure on day four
    • For new workers, the regimen is 20% exposure on day one, increasing 20% thereafter each day.
  • Make allowances for workers who must wear personal protective equipment that retains heat and restricts the evaporation of sweat
  • Schedule hot jobs for cooler parts of the day
  • Consider utilizing cooling vests containing ice packs or ice water to help rid bodies of excess heat


  • Wear light, loose clothing that permits the evaporation of sweat
  • Drink small amounts of water every half hour or so. Don’t wait until you’re thirsty. By then you’re already dehydrated
  • Avoid dehydrating beverages like tea, coffee, or beer
  • When personal PPE must be worn
    • Use the lightest weight clothing and respirators available
    • Wear light-coloured garments that absorb less heat from the sun
    • Use PPE that allows sweat to evaporate
  • Avoid eating hot, heavy meals as they tend to increase internal body temperature by redirecting blood flow away from the skin to the digestive system.
  • Don’t take salt tablets unless prescribed. Natural body salts lost through sweat are easily replaced by a normal diet

Create a Heat Stress Policy

One of the most important steps in heat stress prevention in the workplace is developing a heat stress control policy. This policy should be based on the type of work environment, and it should include guidelines for identifying and responding to heat-related incidents.

In order to develop a heat stress control policy, it’s essential to first determine what type of work environment you are working in. This will make it easier to determine whether or not you need a formal policy in place and what type of procedures should be included in that policy. Two common types of heat common in work environments that require heat stress control policies are process heat and hot weather.

Process Heat

Process heat is generated by equipment that creates excess heat, such as boilers, ovens and furnaces. For these workplaces, the Ontario government recommends employers:

  • Follow the guidance in the American Conference of Governmental Industrial Hygienists (ACGIH) booklet, Threshold Limit Value (TLVs)
  • Develop a heat stress control policy in consultation with the workplace’s joint health and safety committee or worker health and safety representative

Hot weather

Hot weather can also pose a serious risk for workers. If the sun is the reason for the unbearable heat at your place of work, a simplified heat stress control policy beginning May 1, and running until September 30, maybe more suitable.

Consider using the plan when:

  • The humidex on-site reaches or exceeds 35
  • Environment Canada reports air temperature that exceeds 30 C and a humidex of 40
  • Heat waves of 32 C or more are predicted for three or more days
  • The Ontario Ministry of the Environment, Conservation and Parks issues a smog alert

Your Responsibilities as an Employer

The Occupational Health and Safety Act (OHSA) does not specifically cover worker exposure to heat. However, the act does require businesses to protect workers exposed to hot environments.

Employers should develop a written health and safety policy outlining how workers in hot environments will be protected from heat stress. At the minimum, the following should be addressed:

  • Arrange first-aid training for workers
  • Offer a proper work/rest regime for workers
  • Oversee heat stress training and acclimatization for new workers, workers who have been off the job for a while, and workers with medical conditions
  • Monitor the workplace to determine when hot conditions arise and whether workers are staying hydrated
  • Provide ongoing training and education on heat stress and hot environments
  • Modify work practices when workers complain of heat stress

SWS Warning Lights– an integral part of safety requirements

Heat stress is just one part of your health and safety plan. Let us help you with the rest.

As North America’s leader in high-quality warning lights, we can take care of all your warning light needs and make sure that you have the right equipment for keeping your employees safe, no matter the application. Contact us today to learn more.

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