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When is hot too hot?(I) Time:2022/05/10 10:10:00 Hit:14

Keeping workers safe as summer heat approaches requires dedication



Warmer weather is returning to most of the U.S., and for the roofing industry, that means the beginning of the busy season and the all-too-familiar hazards of working in extreme heat. Not only is roofing work physically demanding but it also is performed outdoors in direct sunlight where employees are exposed to excessive heat and environmental conditions that can lead to heat-related illnesses. Yet some roofing professionals underestimate the importance of understandingnand preventing heat-related illnesses.

The likelihood of a roofing worker experiencing a heat-related illness is greater than you may think. The Center for Construction Research and Training’s 2019 study, “Heat-related deaths among construction workers in the United States,” found construction workers experienced about one-third of all heat-related fatalities among all fatal occupational injuries and the trades at highest risk were roofing workers, cement masons, construction helpers and brick masons.


So when is hot too hot? The short answer is: It depends. Part of the issue’s complexity is the term “heat stress,” which people often use generically. The National Institutes for Occupational Safety and Health says heat stress is a combination of several factors, including a worker’s heat exposure from physical activity, environmental factors, and his or her clothing and personal protective equipment. These factors create an increased amount of heat stored by the body, which NIOSH refers to as the net heat load.

NIOSH says the body responds to heat stress by working harder to lose heat through sweating and increased heart rate to maintain a normal core body temperature (about 98.6 F). This physiological response is referred to as heat strain.

The body’s ability to maintain a normal core body temperature is influenced by several factors, including:

  • Air temperature

  • Humidity

  • Radiant heat (such as working in direct sunlight)

  • Skin temperature

  • The speed and temperature of air moving over the body

  • Hydration

  • Clothing

  • Fitness level

  • Age

Preexisting health conditions

Heat stress and the accompanying heat strain can increase the risk for heat-related illnesses.

Heat stress that leads to illness can come in several forms, including heat rash, fainting, heat cramps, heat exhaustion and heatstroke. Heat exhaustion quickly can progress to heatstroke, a life-threatening condition requiring immediate emergency medical response.

Heatstroke can develop after a prolonged period of exposure to a hot, humid environment during a period of a few days, which may or may not involve physical activity. Heatstroke also can develop after heavy exertion. Someone experiencing heatstroke may sweat and have moist skin or skin that is dry and hot. This is important to understand when training workers about the signs and symptoms of heat-related illnesses. Heat-stroke caused by exertion and nonexertion can be life-threatening and require immediate response, including rapid cooling and calling 911.


Preventing heat-related illnesses begins with understanding heat stress and the risk factors. How can you effectively address the hazards of heat stress in your workplace? Start with implementing a heat stress management plan that includes water, rest, shade plus training. Training should highlight the key elements of hydration, shaded rest breaks, acclimatization and an emergency response plan.


Ensuring proper hydration and rehydration after exertion at work and at home are essential steps to preventing heat-related illnesses. Dehydration from working in the heat can be compounded by activities while not at work, and dehydration is the primary cause of heat exhaustion.

Hydration is critical to replacing lost fluids and electrolytes. NIOSH says adequate water consumption (8 ounces every 15 minutes) with regular meals is sufficient to maintain water and electrolyte balance. Workers should not overconsume caffeinated beverages and sugary sports drinks, which are not hydrating.

Rest breaks

Periodic shaded rest breaks during times of high heat are an important part of your heat stress management program. Shaded rest breaks, staggered work hours and earlier start times can help prevent heat-related illnesses.


Heat exposure that may be too hot for one person may not be problematic for another based on personal risk factors and can be difficult to assess on an individual basis. When determining how well a worker has been acclimatized to heat, the answer to what is too hot becomes even more variable. Often, heat stress develops when workers have not worked in heat for a period of time and are not properly acclimatized.

Steve Rowlinson, professor emeritus at the University of Hong Kong, Hong Kong, notes workers who are able to acclimatize to high-heat environments are less likely to suffer from heat stress and heat-related illnesses. He also says acclimatization improves the body’s ability to have a “more efficient heat dissipation system” and “reserve sodium in sweat,” thereby resulting in a worker being more tolerant to heat stress.

Acclimatization takes place gradually over a period of days by a worker increasing the amount of time spent working in a high-heat environment. The Occupational Safety and Health Administration and NIOSH have different recommendations for the amount of days necessary for acclimatization; however, the consensus appears to be between three and seven days.


Preparedness is critically important regardless of the nature of an emergency, and being prepared to respond can be challenging in the industry because job locations and personnel regularly change. Making sure employees are familiar with the location of emergency care is an integral part of a project’s emergency action plan. Training should include recognition of signs, symptoms and risks of heat-related illnesses; prevention; and the buddy system, which assigns each person a partner to look after and report any concerns.

As part of an emergency response plan, your crews will need, at a minimum, materials on-site to facilitate rapid cooling until emergency responders arrive. Rapid cooling is critical during a heat emergency and must be applied quickly when heatstroke is suspected.

Margaret C. Morrissey, author of the 2021 article, “Heat Safety in the Workplace: Modified Delphi Consensus to Establish Strategies and Resources to Protect the US Workers,” highlights the need for rapid cooling such as the TACO method, or tarp-assisted cooling, and notes full-body immersion in water cooler than 62 F is the preferred and most effective method to quickly lower core body temperature. This significantly can improve health outcomes during a heat emergency.

Through pre-job planning and preparedness, this can be achieved on a roof by covering a tarp with ice water or cool water and then wrapping or rolling it around the affected worker’s body until emergency responders arrive. Morrissey also says evaporation using mist and fans is the second most effective method for rapid cooling; ice packs applied to the groin, armpits and neck are less effective but can be used to cool a worker suffering from heatstroke.

In addition to these prevention measures, of equal importance is engaging workers in safety and health programs and practices that instill a sense of ownership and encourage workers to lead and drive safety efforts in the workplace daily.

NRCA provides several resources that can help you train workers about heat safety, and OSHA and NIOSH have developed the OSHA-NIOSH Heat Safety Tool App, a useful resource for planning outdoor work. The app features real-time heat index and hourly forecasts with corresponding risk levels from minimal to extreme risk levels specific to a user’s location. The app also provides information about the signs and symptoms of heat-related illnesses as well as procedures to follow during a heat-related emergency.

In addition, OSHA continues to expand its resources and guidance on its website,, to help employers prevent heat-related illnesses.

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