Employers and Employees Can Work Together to Prevent Heat-related Illness

Michelle Hopkins

Heat-related illnesses can be a major source of concern for employees working in extreme indoor and outdoor heat. Heat-related illnesses typically occur when the body loses its ability to cool due to prolonged or intense exposure to hot temperatures. This sends blood rushing to the skin surface and away from the brain and other organs, leading to their damage, if not addressed. If steps are not taken, an employee may experience the most serious consequences of heat-related illness: heatstroke, permanent disability, or death.1 But together, employers and employees can reduce the risk of heat-related illness by monitoring the heat index, watching for the signs of heat-related illness, and taking preventive action. And these measures can be best accomplished through a workplace safety program that includes a heat-related illness prevention plan.

Validating the need to monitor

Heat-related illnesses are largely preventable; however, more than 70,000 employees became ill and more than 900 employees died as a result of heat exposure between 1992 and 2019.2 Possible contributing factors include:

  • Lack of awareness and understanding
  • Difficulty focusing time and energy on preventive measures
  • An attitude of “I’ll just tough it out” while trying to ignore the heat

Since joining Concentra® in 2000, Ronda McCarthy, MD, MPH, FACOEM, has raised awareness of heat-related illness on the national stage through conferences, webinars, and congressional testimony.3,4 She leads a panel of Concentra medical experts in guiding clinicians and employers on standards and laws related to hazardous workplace exposures, including heat. McCarthy believes building awareness and understanding about heat-related illnesses and dispelling myths about heat stress (e.g., prevention is unnecessary, ineffective, too time-consuming, or excessively expensive) are essential to fostering a safe, healthy work environment.

“Although today there is no national standard on heat stress, the federal Occupational Safety and Health Administration [OSHA] recently announced an advance notice of proposed rulemaking on heat and hot environments,” says Dr. McCarthy.

To raise awareness, OSHA has launched a national emphasis program on harmful heat exposure in the workplace.5 As part of this new enforcement program, OSHA plans to ramp up worksite inspections in several high-risk industries to offset significant rises in heat-related illnesses, injuries, and deaths. This initiative should sound the alarm for employers, as it heightens their need to proactively address heat-related illnesses and injuries by implementing preventive measures to mitigate them.

Recognizing the signs of heat-related illness

Heat-related illness includes heat rash, heat syncope, heat cramps, heat exhaustion, and heatstroke. The most common is heat exhaustion. The affected individual may experience extreme sweating, headache, weakness, nausea, and mood changes. Heat exhaustion calls for rest, water, and shade, and it must be addressed quickly. If not, it can lead to heatstroke, which is life-threatening if not treated emergently.6 Signs of heatstroke may include:

  • High body temperature
  • Red, hot, dry, or sweaty skin
  • Confusion
  • Irrational behavior

Heat cramps can be brought on by inadequate water and salt intake. Resting in a cool place and massaging the cramped area can help, along with drinking more water with electrolytes. Additional signs include convulsions and fainting. It is vital to call 9-1-1 immediately for emergency medical attention and begin immediate cooling measures if heatstroke is suspected.

Other associated heat illnesses include dehydration, a breakdown of muscle called rhabdomyolysis, and kidney disease.6 Through training, supervisors and employees can learn to identify the symptoms of heat illness and their warning signs early. Regular reminders about this information and the seriousness of heat-related illness — particularly during the hot months — will help promote health safety and rapid response to aid employees suffering from heat’s adverse effects.

OSHA and the National Institute for Occupational Safety and Health (NIOSH) have developed a heat safety tool app that can determine when heat-related illness is a possibility based on an hourly heat index. It can also provide precautions and first-aid measures. The heat safety tool app is free to download at the Apple App Store and Google Play

Knowing personal vulnerabilities

According to McCarthy, employees are more vulnerable to heat-related illness if they (1) are unaccustomed to working in hot conditions, (2)  must wear personal protective equipment (PPE) that limits heat transfer, or (3) have personal risk factors, such as:

  • Obesity (body mass index over 30)
  • History of prior heat-related illness
  • Poor physical fitness
  • medical conditions, such as kidney disease, heart disease, diabetes, or asthma
  • Use of certain medications, such as blood pressure prescriptions, diuretics, antidepressants, and sleep aids

Employees who meet any of these criteria and work in hot environments should be encouraged to consult with their doctor or an occupational health provider about the risk of heat illness. They should share details about work duties, work intensity, and length of time spent working in hot temperatures, as well as any special concerns or circumstances. 

Developing heat tolerance

OSHA states that 50 to 70 percent of most outdoor fatalities occur in the first few days of working in warm or hot environments because the body has not sufficiently built heat tolerance. This process of building tolerance is called heat acclimatization. When employees have never worked in a hot environment or haven’t worked in a hot environment for an extended period for any reason, heat acclimatization is necessary. It is also a vital administrative control to prevent heat-related illness. According to NIOSH, effective acclimatization involves gradually exposing employees to hot conditions over a period of days, allowing their body to adjust. For employees new to working in heat, increase exposure time in hot conditions over a 7-to-14-day period based on environmental and individual risk factors. An employer should never increase a new employee’s exposure to heat by more than 20 percent per day.5

Controlling heat exposure

An employer’s heat-related illness prevention plan should include standards that determine when indoor and outdoor heat levels reach a point that places employees at risk. The National Weather Service offers the following recommendations, which employers can use to focus primarily on engineering and administrative work practice controls to mitigate heat exposure.7

Between 80 and 90 degrees Fahrenheit. While the risk of heat illness is lower, employers should take caution and prepare by providing drinking water, making medical services easily accessible, planning training efforts, and acclimatizing employees to the heat. As the heat index goes up, so does the risk of heat-related illness, and prevention measures should intensify.

Between 91 and 103 degrees Fahrenheit. Time to issue a “heat outlook,” as the potential for heat illness exists. Employers should alert employees of high-risk conditions, conduct training, schedule rest breaks in shaded areas, and encourage employees to drink water regularly. 

Between 103 and 124 degrees Fahrenheit. Time to issue a “heat advisory,” as the risk of heat illness is high. Alert employees and limit physical exertion. Start work earlier or split work shifts. Personnel trained in heat stress should be available on site to help monitor employees. Make sure to establish and enforce regular rest periods and establish a buddy system so each employee can partner with a coworker to help monitor the signs and symptoms of heat illness. 

Above 126 degrees Fahrenheit. Risk of heat illness is critical. Do not conduct work that requires protective clothing. Work evening/night shifts. Reschedule nonessential activities and move essential work tasks to the coolest parts of the day. Engineering controls should also be implemented, if possible, such as decreasing air temperature with cooling booths or air-conditioned break rooms, increasing ventilation or decreasing humidity with fans and exhausts, and providing shade in outdoor environments. If these protective measures are not possible, stop work to avoid heat-related illness.

Environmental factors (e.g., humidity, wind, temperature, and radiant heat), clothing, and workload (i.e., metabolic rate) are considered when determining if there is a heat hazard present at a workplace. This can be assessed most effectively using a wet bulb globe thermometer (WBGT).

Establishing a heat illness prevention plan

Along with the OSHA initiative to monitor employers’ efforts to prioritize heat safety, the preventable nature of heat-related illnesses is another reason employers should establish and implement preventive measures. Also, the business costs of not having a plan can be significant — ranging from OSHA citations and productivity losses to serious illnesses and even heat-related deaths. And while obviously less severe than the loss of life, heat stress can also cause a loss of motor skills, mental confusion, and lethargy. The consequences can be serious, but occupational health solutions are available.

“Useful resources are available to develop a heat stress prevention program, including the relevant portion of the OSHA technical manual and the criteria developed by the National Institute of Occupational Safety and Health for a standard on occupational exposure to heat and hot environments,” McCarthy says.8,9

Concentra has created a heat-related illness prevention info sheet with action steps for employers and self-monitoring instructions for employees. Employers and employees can work together on many of the safety recommendations, such as:

  • Understanding the meaning of a heat-related illness
  • Being able to recognize the warning signs
  • Downloading the OSHA-NIOSH heat safety tool app to handheld devices
  • Following guidance to drink water and rest in shaded areas regularly

Concentra also offers comprehensive medical surveillance screening services designed to help employers proactively address risks associated with heat-related illnesses and other occupational health conditions. Contact Concentra for help creating a heat-related illness prevention plan.


  1. Frequently Asked Questions About Extreme Heat. Centers for Disease Control and Prevention. https://www.cdc.gov/disasters/extremeheat/faq.html.
  2. United States Department of Labor. Heat Injury and Illness Prevention in Outdoor and Indoor Work Settings. Occupational Safety and Health Administration. October 27, 2021. https://www.osha.gov/laws-regs/federalregister/2021-10-27.
  3. Concentra webinar: Heat Stress and Employer Readiness. May 27, 2020. https://www.concentra.com/resource-center/webinars/climate-change-heat-stress-and-employer-readiness/.
  4. “Occupational Heat Stress Gets Hearing on Capitol Hill.” Concentra, August 16, 2019. https://www.concentra.com/resource-center/articles/occupational-heat-stress-illness-gets-hearing-on-capitol-hill/.
  5. National Emphasis Program – Outdoor and Indoor Heat-related Hazards. (n.d.). https://www.osha.gov/sites/default/files/enforcement/directives/CPL_03-00-024.pdf.
  6. Centers for Disease Control and Prevention. (2022, May 13). Heat Stress - Heat Related Illness. Centers for Disease Control and Prevention. https://www.cdc.gov/niosh/topics/heatstress/heatrelillness.html.
  7. NOAA's National Weather Service. (2019, December 15). What is the heat index? Heat Forecast Tools. https://www.weather.gov/ama/heatindex.
  8. OSHA Technical Manual, Section 3, Chapter 4: Heat Stress. Occupational Safety and Health Administration. https://www.osha.gov/dts/osta/otm/otm_iii/otm_iii_4.html.
  9. Criteria for a Recommended Standard: Occupational Exposure to Heat and Hot Environments, The National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention. February 2016. https://www.cdc.gov/niosh/docs/2016-106/default.html.