Ask an Expert
How Hot is Too Hot?
How hot can a workplace become? Is a thermometer required to be posted, and how often must water/heat breaks be given?
How hot can a workplace become?
There isn't one specific maximum air temperature because heat stress depends on several environmental factors such as air temperature, humidity, the physical workload and any process heat source that may contribute to heat stress. However, under the general duty clause of the Occupational Health and Safety Act (OHSA), the Ministry of Labour expects employers to take all reasonable measures in the circumstances to protect the health and safety of workers.
Is a thermometer required to be posted?
No, there is no specific requirement under OHSA for a thermometer (which measures temperature) or a Wet Bulb Globe Temperature meter (which measures Humidex) to be posted in a workplace.
How often must water/heat breaks be given?
Under OHSA, there is no specific requirement for water/heat breaks
to be given. However, the Ministry of Labour expects employers to provide
training to workers and to provide water when it's hot and to implement heat
stress control plans and to institute additional breaks when required. When
the Humidex hits 35, a heat stress control plan should be implemented. When
it hits 38 or so, the employer should start giving short breaks and increase
the amount of break time as the Humidex increases. When the Humidex reaches
45, workers may generally have to stop work. There may also be specific
situations that require more individual considerations such as working
outdoors in direct sunlight or working with ovens and furnaces. For more
information, please see the Ministry of Labour's guideline on heat stress.
About the author
Belinda Sutton is a Communications Officer with the Ontario Ministry of Labour.