Heat and Cold Stress

Employees exposed to temperature extremes may be at risk of hot or cold stress, which can cause significant health hazards. If overexposed, their bodies can quickly be overcome with heat-related or cold-related illnesses. Employees that work outdoors (construction, landscaping, delivery services, etc.) are at particular risk.

Where employees could potentially be exposed to extreme temperatures, as an employer you must ensure that:

  • A competent person measures and records thermal conditions at intervals appropriate to assess the changing conditions in the workplace.
  • Employees are instructed to recognize extremes of temperature symptoms and the precautions to follow to avoid injury.
  • You are in compliance with the threshold limit value (TLV) for either heat or cold stress.
  • An adequate supply of fresh drinking water is readily available and that employees have frequent access to it.

While the employer is ultimately responsible for all the provisions mentioned above, the supervisor has a vital role to play in the safety of their teams. As a supervisor, you must:

  • Acquaint your employees with the hazards and control measures associated with their work.
  • Provide the information and instruction necessary to ensure their health and safety.
  • Enforce company safety rules, programs & codes of practice and procedures.

Working in the Heat

During the summer, meteorologists measure the humidex to warn people when temperatures become hazardous. However, the humidex does not take into account the level of activity performed by employees so WorkSafeNB (and some other provinces) require employers to meet the American Conference of Governmental Industrial Hygienists (ACGIH) threshold limit value (TLV for heat stress). The index used by ACGIH is called the Wet Bulb Globe Temperature (WBGT).


Since measuring WBGT can be challenging for employers, the humidex readings can be used as a guide to limit moderate to heavy work activities to cooler times of the day (early morning or evening) or delay them entirely until the outdoor temperature cools off.

Whether working inside or outside during the hot summer months, it is important that employees listen to their bodies and learn to recognize the five main forms of heat stress and their symptoms:

  • Heat rash - "prickly heat rash", tiny, raised blister-like rash on the skin.
  • Heat cramps - painful muscle spasms and excessive sweating.
  • Heat exhaustion - headache, dizziness, weakness, nausea and clammy skin.
  • Heat syncopy - fainting while standing.
  • Heat stroke - severe headache, confusion, delirium, convulsions, loss of consciousness and hot, dry, flushed skin.

There are various factors that can influence the onset of heat related symptoms, including:

  1. Environmental conditions: air temperature, humidity, wind speed and radiant heat (sun).
  2. Intensity of work/work load.
  3. Duration of exposure.
  4. Frequency of work.
  5. Human factors such as physical fitness, age, medications.
  6. Type of clothing.
  7. Degree of acclimatization or becoming accustomed to the work and environmental conditions.

Tips for Preventing Overexposure to Heat and Sun

  • Learn to recognize the signs and symptoms of heat stress in yourself and your co-workers.
  • Acclimatize your body to working in the heat and sun.
  • Drink plenty of water (about two glasses of water before starting work and one cup (250 ml or more)) about every 15 to 20 minutes during work) and get adequate nutrition.
  • Avoid caffeine, alcohol, and drugs.
  • Wear light-coloured, loose-fitting clothing made of breathable fabric.
  • Wear a wide-brimmed hat. If a hard hat is required, attach a piece of light-coloured fabric to the back and sides to shade your neck.
  • Take rest breaks in a cool or ventilated area. Take more breaks during the hottest part of the day or when doing heavy work. Allow your body to cool down before beginning again.
  • Schedule work to minimize heat exposure. Do the hardest physical work during the coolest part of the day.
  • Use sunscreen with an SPF of at least 30. You need to apply at least one ounce (29.58 ml) 30 minutes before sun exposure to ensure that you get the full SPF of a sunscreen. Re-apply it every two hours throughout the day.(Skin Cancer Foundation recommendation)
  • Wear eyewear that provides UV protection.

Working in the Cold

Cold weather can be a serious hazard. Construction, trucking, farming and logging are examples of occupations where the potential for hypothermia and frostbite exists. There are also safety problems associated with working in cold environments - ice, snow, burns from contact with cold metal, slowed reaction time and snow blindness.

Learn to recognize the warning signs of hypothermia:

  • Severe shivering (In severe cases, shivering may stop - seek medical attention immediately).
  • Pain in extremities (hands, feet, ears).
  • Reduced mental capacity (confusion, difficulty speaking, etc.).

For frostbite, in mild cases, the symptoms include inflammation of the skin in patches accompanied by slight pain. In severe cases, there could be tissue damage without pain, or there could be burning or prickling sensations resulting in blisters.

Tips for Preventing Overexposure to Cold

  • Wear proper clothing in layers.
    • First layer - snug-fitting and of a material that allows sweat to escape (silk or polypropylene).
    • Second layer - loose and warm (fleece, wool or down).
    • Third layer - windproof and waterproof (nylon or Gore-Tex).
  • Wear mittens when working in temperatures below -17°C, gloves for light work below 4°C and -7°C for moderate work, a warm knit hat or a liner under a hard hat, and footwear that is insulated, slip-resistant and waterproof.
  • Take frequent measures of temperature with the wind factor.
  • Take warm-up breaks in a shelter.
  • Pace work to prevent excessive sweating as the moisture will speed cooling of the body. Add or remove layers as appropriate.
  • Stay hydrated. Drink water or warm, sweet beverages (sports-types drinks). Avoid caffeinated drinks.
  • Know the signs of hypothermia and frostbite. Use the buddy system to watch for signs shown by your co-workers.

General Regulation - Occupational Health and Safety Act
N.B. Reg. 91-191


Section 4 Drinking Water

4. (1) An employer shall ensure that sufficient potable water for drinking is readily available and that it meets the standards set out in the "Guidelines for Canadian Drinking Water Quality" , Sixth Edition, published by authority of the Minister of National Health and Welfare, 1996.

(2) Where drinking water is not taken directly from a water pipe, an employer shall ensure that it is kept in an adequately covered container and that, if used by more than one employee, the container is equipped with a drain faucet.

(3) An employer shall ensure that individual sanitary drinking vessels or cups are provided, except where the drinking water is delivered in an upward jet from which an employee may drink.

(4) Where outlets exist for both drinking water and water not suitable for drinking, an employer shall ensure that the outlets are appropriately and clearly labelled.

[N.B. Reg. 2001-33, s. 2]


Section 22 Extremes of Temperature

22. Where an employee is exposed to work conditions that may present a hazard because of extreme heat or extreme cold, an employer shall ensure that

(a) a competent person measures and records the thermal conditions at frequent intervals and makes the findings available to a committee, if any, and to an officer on request, and

(b) the threshold limit values for protection against heat stress and cold stress are followed as well as the work-rest regimen for heat and the work-warming regimen for cold and other advice found from pages 125 to 140 of the ACGIH publication "1997 Threshold Limit Values for Chemical Substances and Physical Agents and Biological Exposure Indices".

[N.B. Reg. 2001-33, s. 6]

Section 23

23. (1) Where an employee is exposed to work conditions that may present a hazard because of excessive heat, an employer shall ensure that a competent person instructs the employee in the significance of symptoms of heat stress such as heat exhaustion, dehydration, heat cramps, prickly heat and heat stroke and in the precautions to be taken to avoid injury from heat stress.

(2) Where an employee is exposed to work conditions that may present a hazard because of excessive cold, an employer shall ensure that a competent person instructs the employee in the significance of symptoms of cold stress such as severe shivering, pain in the extremities of the body and reduced mental awareness and in the precautions to be taken to avoid injury from cold stress.