Heat Stress

With summer around the corner and potential soaring temperatures, heat stress can be a real threat to workers’ health and well-being.  

The average human body naturally maintains a temperature between 36°C and 38°C. Sweating cools our bodies down but if you work in a hot environment this might not be enough to provide relief from the heat. 

“Working in hot conditions puts stress on our body’s cooling system,” said Sari Sairanen, Director Health, Safety and Environment. “High temperatures and humidity stress the body’s ability to cool itself and heat illness becomes a special concern during hot weather.” 

The three major forms of heat illness are; heat cramps, heat exhaustion and heat stroke. A heat stroke can be a life threatening condition but it is one that is mitigated through engineering and administrative controls, including: the use of insulating and reflecting barriers, air-conditioned rest areas and mechanical assistance to reduce the physical demands of work. Other mechanisms for preventing heat stress are increased frequency and length of breaks, training workers to recognize symptoms of heat stress and possibly scheduling hot jobs to cooler times of the day.

In advocating for these and other strategies to manage work in hot conditions, members, health and safety reps and the union can help to collectively negotiate more permanent solutions. Unifor has made several health and safety gains by negotiating solutions that range from isolating hot equipment to implementing mandatory cooling down periods and revising work schedules during heat waves.

In 2001, the heat stress related fatality of a member at Weston Bakeries led to an inspection of the workplace by the Ontario Labour Ministry. The inspection resulted in the plant being shut down temporarily and heat stress education and training for workers was mandated. This came on the heels of workers expressing concerns about excess heat, lack of sufficient cool water and inadequate heat stress breaks.

“We need to ensure workers are aware of their right to refuse work, including work which can endanger them,” said Vinay Sharma, National Representative for Health and Safety. “In addition to environmental and work scheduling controls, workers should have access to personal protective equipment, like water-cooled jackets and reflective clothing in high radiant heat situations as may be required.”

Unifor is currently working with University of Ottawa to develop heat exposure limits to safeguard the health and well-being of older adults and those with common chronic disease such as type 2 diabetes and/or hypertension during rest and physical activity.  We need older adults (50+) with and without type 2 diabetes and/or hypertension from the Ottawa area to participate in our study.

If you would like to volunteer, please email @email

For more information about heat stress and ways to address it, please review this PDF document and be sure to contact your local health and safety workplace representative.