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Heat Hazards

Construction workers, who often work outdoors in direct sunlight or in hot, enclosed spaces, are at risk for heat-related illnesses and, in severe cases, death. Rising global temperatures in recent decades increase that risk. However, these illnesses and deaths are preventable.

The following resources contain information about heat hazards in construction, and ways to prevent related illnesses.

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Heat Illness Prevention Planning
Employee Training

What’s the risk?

Signs and symptoms of heat-related illness

Factors that increase risk

Training resources

Acclimatization
  • Adjusting to Work in the Heat: Why Acclimatization Matters (NIOSH Science Blog, 2014)
  • Acclimatization (NIOSH)
  • NEW! Preventing Heat-Related Deaths in Construction: The Importance of Acclimatization (OSHA-CPWR Alliance)
  • Protecting New Workers (OSHA) – English, Spanish
    To protect workers from heat-related illness, employers should do the following:
    • Schedule new or returning workers to work shorter amounts of time working in the heat, separated by breaks, in heat stress conditions.
    • Give new or returning workers more frequent rest breaks.
    • Train workers about heat stress, symptoms of heat-related illness, and the importance of rest and water.
    • Monitor workers closely for any symptoms of heat-related illness.
    • Use a buddy system and don’t allow new or returning workers to work alone.
    • If workers talk about or show any symptoms, allow them to stop working. Initiate first aid. Never leave someone alone who is experiencing symptoms!

    These increased precautions should last for 1-2 weeks. After that time, new and returning workers should be acclimatized to the heat and can safely work a normal schedule.

Exposure Monitoring

Weather monitoring

Active measurement
Wet Bulb Globe Temperature WBGT uses temperature, humidity, wind, solar radiation, and other weather parameters. It’s a particularly effective indicator of heat stress for active populations such as outdoor workers.

Water, Rest, Shade
  • Water. Rest. Shade. (OSHA) – English, Spanish
    Water
    Employers should provide cool water for workers to drink. Proper hydration is essential to prevent heat-related illness. Workers should not rely on feeling thirsty to prompt them to drink. They should be reminded to drink on a regular basis to maintain hydration throughout their shift and beyond.

    For those working two hours or more, also provide access to additional fluids that contain electrolytes. For short jobs, cool potable water is sufficient. Workers should be encouraged to drink at least one cup (8 ounces) of water every 20 minutes while working in the heat not just if they are thirsty. For longer jobs that last more than two hours, employers should provide electrolyte-containing beverages such as sports drinks. Workers lose salt and other electrolytes when they sweat. Substantial loss of electrolytes can cause muscle cramps and other dangerous health problems. Water cannot replace electrolytes; other types of beverages are needed. Water or other fluids provided by the employer should not only be cool, but should also be provided in a location that is familiar to the workers, near the work, easy to access, and in sufficient quantity for the duration of the work.

    Rest
    When heat stress is high, employers should require workers to take breaks. The length and frequency of rest breaks should increase as heat stress rises. In general, workers should be taking hourly breaks whenever heat stress exceeds the limits shown in Table 2 under Determination of Whether the Work is Too Hot section on the Heat Hazard Recognition page.

    Breaks should last long enough for workers to recover from the heat. How long is long enough? That depends on several factors including environmental heat (WBGT) and the worker’s physical activity level, as well as the individual worker’s personal risk factors. The location of the breaks also matters. If workers rest in a cooler location, they will be ready to resume work more quickly. Breaks should last longer if there is no cool location for workers to rest. Some workers might be tempted to skip breaks. In hot conditions, skipping breaks is not safe! Employers should make sure that workers rest during all recommended break periods.

    Shade
    Workers should be given a cool location where they can take their breaks and recover from the heat. Outdoors, this might mean a shady area, an air-conditioned vehicle, a nearby building or tent, or an area with fans and misting devices. Indoors, workers should be allowed to rest in a cool or air-conditioned area away from heat sources such as ovens and furnaces.

  • Take Water Breaks infographic (CPWR) – English: JPEG, PDF; Spanish: JPEG, PDF
PPE, Cooling Systems and Additional Solutions
Rescue Planning
  1. Heat Related Illness & First Aid (OSHA) – English, Spanish
  2. Heat-Related Medical Emergency Infographic ZIP (OSHA) English, Spanish
Employer Responsibilities/OSHA Guidance & Enforcement