By: June Mills

When most of us think of the summer, images of the beach, barbecuing, and other outdoor activities come to mind. While these activities are part of what makes summer so enjoyable, a larger part of many of our summers is inevitably spent in the workplace. With heat waves affecting regions across Canada this summer, it is helpful to take a refresher on how temperature is regulated in the workplace.

In Nova Scotia, under the Occupational Heath and Safety Act, clause 13(1), employers have a duty to take every reasonable precaution to ensure the health and safety of persons in the workplace. Furthermore, clause 2.3(h) of the Workplace Health and Safety Regulations, requires all employers to comply with the threshold limit values for exposure to physical agents as listed in the American Conference of Governmental Industrial Hygienists on Threshold Limit Values and Biological Exposure Indices. One of the physical agents listed is heat stress.

What is heat stress?

Heat stress is defined by the Nova Scotia Occupational Health and Safety Division as “the build up of heat in the body to the point where the body’s thermostat has difficulty maintaining normal internal body temperature. When the body is unable to cool itself through sweating, serious heat illnesses may occur.”

According to the Canadian Centre for Occupational Health and Safety, heat in a working environment can come from many sources:

  • Hot or molten material (foundries, bakeries, glass factories etc.)
  • Sunshine (construction, agriculture, open-pit mining etc.)
  • High humidity (laundries, restaurants, kitchens etc.)

While most of us enjoy the summer heat, when a work environment becomes too hot the body’s coping mechanisms can become overwhelmed and lead to heat-related illnesses.

The Ontario Ministry of Labour, provides a helpful summary of various heat-stress related illnesses, citing the causes, symptoms, treatment and prevention. Among such heat-stress related illnesses is heat rash, heat cramps, fainting, heat exhaustion and heat stroke.

What temperature is too hot?

In Nova Scotia, the Workplace Health and Safety Regulations mandates compliance with the threshold limit values for heat stress as set out by the American Conference of Governmental Industrial Hygienists (ACGIH).

There are numerous factors to consider, when conducting a heat stress assessment in a work environment. Factors include: clothing required on the job, level of physical activity and percentage of the work day being physically active.

The actual measurement and assessment of factors that contribute to heat stress is complicated and requires specialized equipment. The Nova Scotia Occupational Health and Safety Division recommends this assessment be conducted by professional consultants.

How can heat stress be prevented?

According to the Nova Scotia Occupational Health and Safety Division, employers must have a heat stress strategy if the workplace presents environmental conditions that put employees at risk of adverse health effects due to high temperatures.

A heat stress strategy may include:

  • Employee education and training
  • Heat stress assessment
  • Heat stress controls

Heat stress controls are measures that work to control temperature in the workplace. Examples of heat stress controls can be broken into three categories: engineering controls, administrative controls and protective clothing. Examples of each are:

  • Engineering controls:
    • Air-conditioning
    • Reflective heat barriers
  • Administrative controls
    • Scheduling work during cooler parts of the day
    • Frequent breaks
    • Providing cold water and medical oversight
  • Clothing:
    • Water insulated clothing
    • Light colored clothing
    • Head covering

 Working in an Office

Nova Scotia Occupational Health and Safety Division recommends referring to a humidex chart as a guideline for working in an office environment. For further information on the humidex, the Canadian Centre of Occupational Health and Safety is a helpful resource.

 A Note on Acclimatization

When working in a hot environment, it takes time for your body to acclimatize to the heat. Acclimatization is the body’s way to adapt to a new thermal environment. The Canadian Centre for Occupational Health and Safety states that complete heat acclimatization generally takes 6-7 days. However, this time period may vary depending on the person’s physical fitness, work training, and work experience. In addition, health conditions or medications may also interfere with a worker’s ability to acclimatize. Consequently these workers may require longer periods of acclimatization.


While most of us enjoy the summer heat, working in hot conditions can pose potentially serious health risks. As such, it is helpful to stay informed on the causes of heat stress and ways to prevent it, especially given the recent heat waves hitting Nova Scotia.

Always remember, everyone has a right to a safe working environment!