Outdoor Work in Hot Weather: Recognizing and Treating Heat-Related Emergencies

Every summer, Quebec workers fall victim to heat-related emergencies on construction sites, in greenhouses, on roofs, and in poorly ventilated warehouses. According to the Canadian Centre for Occupational Health and Safety (CCOHS), heat exposure is one of the most underestimated occupational hazards — yet, untreated heatstroke can cause permanent brain damage or death in minutes. Knowing first aid for outdoor heat emergencies is an essential skill for any supervisor and designated first aider.

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The 3 Stages of Heat-Related Emergencies

Heat-related emergencies progress through three distinct stages — each with its own signs, first aid, and level of urgency. Recognizing them early is crucial.

Stage 1: Heat Cramps

Heat cramps are the first warning sign. They manifest as painful muscle spasms, most often in the calves, thighs, or abdomen. They occur in workers who sweat profusely and lose electrolytes without replacing them.

First aid:

• Stop physical activity immediately and move the worker to a shaded or cool area.
• Have them drink cool water or an electrolyte drink in small sips.
• Apply gentle pressure or lightly massage the cramped muscle.
• Do not resume work until the cramps have completely disappeared.

Stage 2: Heat Exhaustion

Heat exhaustion is a moderate medical emergency. The body begins to lose control of its internal temperature. Characteristic signs include:

• Pale, cool, clammy skin (excessive sweating)
• Intense weakness, dizziness, headaches
• Nausea, sometimes vomiting
• Rapid but weak pulse
• Elevated body temperature but below 40°C (104°F)
• Slight confusion or unusual behavior

First aid:

1. Get the worker out of the heat immediately — look for air conditioning or shade.
2. Lay them on their back, legs slightly elevated if possible.
3. Remove unnecessary clothing (jacket, helmet if there's no risk of falling).
4. Apply cool, wet compresses to the forehead, neck, and armpits.
5. If conscious and able to swallow, have them drink cool water — about 250 ml (8 oz) every 15 to 20 minutes.
6. Call 911 if symptoms do not improve within 15 to 30 minutes or worsen.

Never leave alone a worker suffering from heat exhaustion. Stay with them until help arrives or until they fully recover.

Stage 3: Heatstroke — Absolute Medical Emergency

Heatstroke is the most severe and life-threatening form. The body's thermoregulation mechanism has completely shut down. Body temperature exceeds 40°C (104°F).

Distinct signs of heatstroke compared to heat exhaustion:

• Hot, red, and DRY skin — the worker has stopped sweating
• Severe confusion, disorientation, irrational behavior
• Possible loss of consciousness
• Rapid and strong pulse
• Rapid and shallow breathing

Call 911 immediately. Heatstroke is a life-threatening medical emergency. While waiting for help:

1. Move the worker to the coolest possible place.
2. Remove as much clothing as possible.
3. Liberally wet the entire body with cool water and fan them.
4. Apply ice (wrapped in a cloth) to the neck, armpits, and groin — these areas contain large arteries that cool the blood quickly.
5. Do not give anything to drink if the person is confused or unconscious — risk of choking.
6. If they lose consciousness and are not breathing normally, begin CPR.

Workers Most at Risk

Certain individuals are particularly vulnerable to heat emergencies:

• Workers in the first week of a heatwave (insufficient acclimatization)
• Workers wearing protective equipment (suits, masks) that prevent evaporation
• New workers and older workers
• People taking certain medications (diuretics, antihistamines, some antidepressants)
• Workers who have previously experienced heatstroke

Prevention: The Employer's Responsibility

Under the Act respecting occupational health and safety, employers have an obligation to protect their workers from heat-related risks. Basic measures recommended by the CNESST:

• Fresh water continuously available nearby (minimum 250 ml every 20 minutes)
• More frequent breaks in the shade or air-conditioned areas during heatwaves
• Task rotation to limit prolonged exposure
• Gradual acclimatization for new workers (gradual increase in exposure over 7 to 14 days)
• Designated first aider trained to recognize heat emergencies

Key Takeaways

Outdoor work heat emergencies progress through three stages — cramps, exhaustion, heatstroke — and each requires a different response. The key is to intervene at the first signs, before the situation escalates. Heatstroke is a life-threatening emergency requiring immediate 911 intervention and rapid active cooling. Supervisors, designated first aiders, and workers: knowing these actions can save a colleague's life this summer.

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Disclaimer: This article is provided for educational purposes only. It does not replace the advice of a healthcare professional or certified first aid protocols. In case of emergency, call 911.