Heat Stress at Work: What Ontario Employers Need to Know (and Do Now)
- Shaelyn Ferguson
- Jun 4
- 2 min read
As temperatures rise across Ontario, heat stress (or heat illness) becomes more than a seasonal inconvenience—it becomes a serious workplace hazard. While Ontario does not have heat-specific legislation, employers still carry clear legal responsibilities under the Occupational Health and Safety Act (OHSA) to protect workers illness and injury. Understanding legal requirements and best practices can help employers reduce risk, protect their workers, and avoid liability.
The Legal Duty: What the OHSA Requires
The Occupational Health and Safety Act has what is widely referred to as the General Duty Clause, which requires employers to take every precaution reasonable in the circumstances to protect workers. This includes managing environmental factors like heat. The General Duty Clause applies to supervisors as well, who are also required to ensure workers follow safe work practices and use protective measures.
Even without a specific heat stress regulation, the Ontario Ministry of Labour, Immigration, Training and Skills Development (MLITSD) can enforce heat-related protections under:
Section 25(2)(h): Employer duty to take every precaution reasonable in the circumstances for the protection of a worker.
Section 27(2)(c): Supervisor duty to take every precaution reasonable in the circumstances for the protection of a worker.
In practical terms, this means employers and supervisors must identify and control heat stress risks in their workplaces.
No Heat Laws Doesn't Mean No Responsibility
A common misconception is that if there is no explicit law for heat hazards, there is no enforceable requirement. This is incorrect.
Guidance provided by organizations like the Occupational Health Clinics for Ontario Workers (OHCOW) and the Government of Ontario make it clear that employers are expected to:
Assess heat exposure risks,
Implement controls,
Monitor conditions,
Train workers.
Additionally, standards like the ACGIH's Threshold Limit Values (TLVs) for heat stress are widely recognized and are often used to evaluate whether employers are meeting their legal obligations.
Understanding Heat Stress Risks
Heat illness occurs when the body can no longer cool itself effectively. When exposed to extreme heat, the body's core temperature rises, increasing the heart rate to dangerous levels. This can lead to:
Heat rash,
Dehydration,
Fainting,
Cramps,
Heat stroke (a medical emergency).
Risk factors include:
High temperatures and humidity (humidex),
Heavy physical work,
Lack of acclimatization,
Inadequate hydration,
PPE that traps heat.
Tools like OHCOW's Heat Stress Toolkit can help employers assess risks and choose appropriate controls.
How Correct Compliance Can Help
Building and maintaining a Heat Stress program takes time, expertise, and ongoing monitoring. Correct Compliance supports Ontario employers with:
Heat Stress Program Development: Custom policies aligned with the OHSA and industry standards.
Program Implementation: Onsite rollout, training and documentation.
Workplace Heat Assessments: Using recognized tools and methodologies.
Site Audits and Compliance Reviews: Identify gaps and ensure readiness for inspections.
Supervisor and Worker Training: Practical, compliant, and easy to apply.
Whether you're starting from scratch or updating an existing program, Correct Compliance can help ensure your workplace is safe and up-to-date.
Heat illness risks escalate quickly during Ontario summers. Waiting until temperatures spike can leave workers vulnerable and employers exposed to fines and orders. A proactive approach protects your people and your business.
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