Employer Advice on Managing Heat Stress in the Workplace

  • Workplace Health & Safety
construction worker suffering heat stress
Michelle Ann Zoleta

Michelle Ann Zoleta, Health & Safety Team Manager

(Last updated )

Under the Occupational Health and Safety laws, it is the employer’s general duty to take all reasonable precautions for the health and safety of their employees. This includes protecting staff working in hot conditions from heat stress and heat stroke.  

Given the high temperatures southern regions of Canada experience during summer, it is important that employers have a heat stress plan in place to protect their staff. 

What is heat stress?

Heat stress occurs when your body heats up faster than it can cool itself. Usually, sweating cools down our bodies. But this might not suffice when you work in a hot and humid environment. In this case, sweating causes dehydration as the body loses fluids and salt through sweat. As the body cannot get rid of excess heat, its core temperature increases, and the heart rate goes up.


Outdoor workers are typically exposed to occupational heat stress, which impacts workers’ overall health and safety, and lowers productivity, resulting in economic loss.

Heat stress can lead to heat disorders, such as heat cramps, heat exhaustion, and heat stroke (which can be fatal if not treated immediately).  

What are the first signs of heat stress & heat exhaustion?

Watch out for the following signs:

  • Excessive sweating
  • Dizziness
  • Nausea
  • Irritability
  • Fainting
  • Fatigue
  • Muscle cramps
  • Headache and confusion
  • Heat rash
  • Trouble breathing 

What factors can cause heat stress?

A major cause is the work environment. This includes factors such as radiant heat due to direct or indirect sunlight or high humidity. 

When the air temperature in the workplace is hotter than the skin temperature, it can also cause the body to overheat. Another cause is the nature of work. More active tasks will produce more heat in the body. 

A third main cause for heat stress could be health of the worker. Their bodies may not react well to overheating due to preexisting medical conditions or advanced age, obesity, or insufficient water intake. Conditioning also makes a difference. If the worker is not used to working in hot environments, they may be prone to heat stress. Inappropriate personal protective equipment and/or excess clothing are other causes. 

How can you protect your workers from heat stress?

To safeguard your staff from heat disorders, you should first conduct a risk assessment of your workplace. Once you identify the hazards, you can use the hierarchy of safety controls to make the necessary changes to your workplace. The hierarchy of controls ranks different methods of controlling hazards according to their effectiveness.

How do you keep workers cool in the heat?

Step I: Elimination or substitution of the risk

This is the most effective safety control. You should ask yourself — is it possible to carry out the work in a cooler environment?  If it is, then you can eliminate the risk of heat stress by changing the work environment.

Step II: Engineering controls

This method involves modifying your workplace to minimize the hazard. Examples of engineering controls to reduce heat stress would include:

  • Installing air conditioners to reduce the temperature
  • Creating shaded workspaces and air-conditioned rest areas
  • Using machines for heavy lifting work
  • Insulating hot surfaces to reduce radiant heat
  • Ensuring you exhaust any steam and hot air produced during operations 

Step III: Administrative controls

You can also alter your work policies and procedures to minimize the threat of heat stress. For instance, you could:

  • Create a heat stress plan for hot summer days
  • Increase the frequency and duration of breaks
  • Provide cool drinking water at the work site and remind staff to drink a cup of water at least every 15 to 20 minutes even if they are not thirsty
  • Schedule exhausting jobs to cooler times of the day such as early morning or late afternoon or night
  • Bring in more workers or slow down the pace of work
  • Advise workers to avoid direct sunlight
  • Train workers to recognize the signs of heat stress
  • Start a ‘buddy system’ as workers are not likely to notice their own symptoms
  • Ensure workers trained in first aid are available and on-site
  • Make an emergency response plan for heat-related illnesses
  • Ensure your staff has time to acclimatize to a modified intensity of work
  • Advise workers who have a medical condition or are pregnant to consult their doctor regarding working in the heat and make necessary accommodations for them

Step IV: Personal Protective Equipment (PPE)

This is the least effective control and must be used in combination with other safety controls. Make sure your workers wear light and breathable summer clothing. Their heads should also be covered to avoid exposure to direct sunlight. 

Your staff working in very hot environments must wear heat-reflective clothing or water-cooled suits. Avoid chemical protective clothing, which isn’t breathable. If workers must wear it, they should keep an eye out for early signs of heat stress. 

Make sure the PPE your staff uses has been tested and is working properly. 

How can I help new workers adjust to hot environments?

For workers with no experience of working in hot environments, you could gradually increase the activity level over one to two weeks. Or you could gradually increase the time spent in the hot environment. 

Even workers with experience will gradually need to re-adjust to the heat if they have been ill or away from work for 9 or more days.

How and when to create a heat stress plan?

You should create a heat stress plan based on your work environment. For workplaces, such as smelters, bakeries, etc., the Ontario Ministry of Labour recommends employers follow the guidelines in the American Conference of Governmental Industrial Hygienists (ACGIH) booklet, Threshold Limit Value (TLVs).

Employers are also advised to set up a heat stress control plan in consultation with their workplace joint health and safety committee or worker health and safety representative. Employers in Ontario are advised to create and use a hot weather plan between May 1 and September 30 every year.  

The governments of British Columbia and Alberta also provide guidance and resources on their websites for managing heat stress at work.

Please note that this article does not replace the Occupational Health and Safety legislation in your province. It should not be used or considered as legal advice. Health and safety officers apply the law based on the facts in the workplace. 

Do you need help creating a heat stress plan for your workplace?

Whether you need assistance developing company policies, have an HR or health & safety query or are struggling with an employee issue – Peninsula can help.

We will help you streamline your processes, update policies and workplace documentation, and ensure you are compliant with  laws and protected from litigation. We have a team of consultants available 24/7 via telephone to answer all your queries. We also offer a smart HR software to make your daily HR and OHS tasks quick and convenient.

To learn more about how our services can benefit your business, call an expert today at 1 (833) 247-3652.

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