Elements of a Comprehensive Heat Stress Program

Quick Tips #400

According to the Occupational Safety and Health Administration (OSHA), in 2014 approximately 2,600 workers succumbed to heat related illnesses. And 18 of these incidents resulted in deaths caused by heat stroke. With better planning and awareness training regarding the signs and symptoms of heat induced illnesses, many of those cases could have been avoided. Currently there is no specific OSHA standard that covers working in hot environments. However, OSHA’s General Duty clause, Section 5 (a)(1) requires employers to provide a workplace free from recognized hazards that could cause death or serious physical harm to their employees. Employers with work tasks that involve elevated temperatures need a heat stress program.

Any worker exposed to hot and humid conditions, either outdoors like construction, landscaping and surface mining or indoors in hot environments such as, bakeries, boiler rooms and foundries are at risk of heat stress. Putting your plan into effect when the heat index temperature is above 80°F and adjusting the workload based on current and anticipated conditions are key components of any comprehensive heat stress program.

Heat Stress Prevention Plan

Here are seven key elements to an effective heat stress prevention plan:

  • Written policy
  • Hierarchy of controls
  • Heat acclimatization plan
  • Environmental monitoring
  • Training
  • Hydration
Written Heat Stress Policy

Being pro-active by having an established heat stress prevention policy in place before the heat index level rises is critical. Elements of a written heat stress policy include:

  • Purpose / Scope
  • Responsibilities
    • Supervisors
    • Employees
  • Safe work procedures
    • Heat acclimatization plan
    • Hydration
    • Medical monitoring
    • Environmental monitoring
  • Training
    • Signs and symptoms
    • Emergency procedures
  • Program evaluation
Hierarchy of Controls

OSHA recognizes the “Three Lines of Defense” as a way of thinking about and applying specific actions to reduce or eliminate potential exposures to identified hazards. This is a commonly used and understood practice within the safety community. In this philosophy, you always apply the most effective method first, working down from there. This begins with eliminating or engineering the hazards out, then implementing administrative controls such as policies and procedures to control employee exposures to hazards, and lastly if the first two lines of defense are not feasible, while these controls are being implemented, or in emergencies, incorporating the use of personal protective equipment (PPE) is a must. PPE can be used in conjunction with engineering controls, administrative controls and sound manufacturing practices to reduce employee exposure to the heat.

Engineering Controls

Engineering controls are changes to equipment or to the work process that eliminate or isolate hazards. They are the most effective method to control hazards because they do not depend on people to provide protection. The best way to prevent heat-related illness is to make the work environment cooler. There are a variety of engineering controls that address the actual source of heat and eliminate the workers heat exposure. Some examples of engineering controls that can be used to reduce employee exposure to heat include:

  • Air conditioning
  • Increase general ventilation
  • Cooling fans
  • Local exhaust ventilation
  • Insulation of hot surfaces
Administrative Controls

OSHA considers administrative controls as measures aimed at reducing employee exposure to hazards. If it is not possible or practical to eliminate sources of high heat, employers can establish work policies and procedures to reduce the length of time workers are exposed to heat hazards. These are considered to be the second most effective way to control hazards. Some examples of administrative controls for workers exposed to a high heat environment include:

  • Having workers who have strenuous jobs rotate in and out of the hot environment to reduce exposure
  • Adjusting the work schedule, having strenuous work done during cooler parts of the day such as early morning or evenings, or possibly rescheduling activities for a cooler forecasted day if feasible
  • Adjusting the work/rest schedule to include more frequent breaks allowing employees to leave the hot environment
  • Having additional workers to reduce the physical demands during hot weather
  • Providing heat stress training for all workers who are exposed to high heat
Personal Protective Equipment

Personal protective equipment (PPE) is the third and always last line of defense. What PPE provides is a barrier between the worker and the heat source. Examples of heat stress protective PPE include cooling hats, sweatbands and hardhat cooling products like neck shades, bandanas, sun shields and cooling pad inserts. Other forms of PPE include reflective clothing, body cooling garments and microclimate vests. There are several kinds of cooling vests for heat stress and selecting the best style for your application will be site specific. Some examples of microclimate cooling vests include:

  • Liquid cooled vests – circulates cooled liquid
  • Evaporate garments – soaked in cold water and relies on evaporation for cooling
  • Passive change style vests – equipped with ice packs
Heat Acclimatization Plan

Employers should have an acclimatization program for new, temporary and returning workers coming off an extended absence who work in hot environments. New workers need a period of time to get accustomed to the heat. To accomplish this, an abbreviated work schedule that gradually increases their heat tolerance should be instituted. The lack of acclimatization has been shown to be a major factor associated with worker heat-related illness and death.

Medical Monitoring

It’s important for employers to institute a medical monitoring program for employees who work in hot environments. The program should include components of medical screening and surveillance with the goal of early detection of signs and symptoms of heat-related illnesses.

Suggested components of a comprehensive medical monitoring program for employees at risk for heat-related illnesses should include employee training, preplacement medical examinations, periodic follow-up evaluations and heat-related illness incident reporting.

Environmental Monitoring

It’s important to track weather daily at work sites when forecasts are predicting day time highs to reach 80°F or higher. Both the heat index and wet bulb globe temperature (WBGT) are used to evaluate environmental temperature in hot environments. WBGT is calculated by measuring dry air temperature, humidity and radiant energy which is used to determine a thermal load on the employee. Because of certain limitations, many small businesses may not have the means to determine WBGT. In those instances, the heat index is a practical substitute.

Apparent Temperature (What it Feels Like)
(Degrees Fahrenheit/Degrees Celsius)
0% 64°/18° 69°/21° 73°/23° 78°/25° 83°/28° 87°/30° 91°/33° 95°/35° 99°/37°
10% 65°/18° 70°/21° 75°/24° 80°/26° 85°/29° 90°/32° 95°/35° 100°/38° 105°/41°
20% 66°/18° 72°/22° 77°/25° 82°/27° 87°/30° 93°/34° 99°/37° 105°/41° 112°/44°
30% 67°/19° 73°/23° 78°/25° 84°/28° 90°/32° 96°/35° 104°/40° 113°/45° 123°/51°
40% 68°/20° 74°/23° 79°/26° 86°/29° 93°/34° 101°/38° 110°/43° 122°/50° 137°/58°
50% 69°/21° 75°/24° 81°/27° 88°/31° 96°/35° 107°/42° 120°/49° 135°/57° 150°/66°
60% 70°/21° 76°/24° 82°/27° 90°/32° 100°/38° 114°/45° 132°/56° 149°/65°  
70% 70°/21° 77°/25° 85°/29° 93°/34° 106°/41° 124°/51° 144°/62°    
80% 71°/22° 78°/25° 86°/29° 97°/36° 113°/45° 136°/58° 157°/69°    
90% 71°/22° 79°/26° 88°/31° 102°/39° 122°/50° 150°/66° 170°/77°    
100% 72°/22° 80°/26° 91°/33° 108°/42° 133°/56° 166°/74°      

Likelihood of heat disorders with prolonged exposure or strenuous activity:

Heat Index Risk Level Protective Measures
Less than 91°F (32°C) Lower (caution) Basic heat safety and planning
91° to 103°F (32° to 39°C) Moderate Implement precautions and heighten awareness
103° to 115°F (39° to 46°C) High Additional precautions to protect workers
Greater than 115°F (46°C) Very high to extreme Triggers even more aggressive protective measures


The heat index is a measure of how hot it really feels when relative humidity is factored in with the actual air temperature. The heat index is a good option for many outdoor work environments.

An easy method to monitor the heat index is to download the OSHA-NIOSH Heat Safety Tool app for smart phones so that each job site can calculate the heat index which displays a risk level to outdoor workers. The app provides reminders about protective measures, drinking proper amounts of fluids, scheduling rest breaks, what to do in an emergency, adjusting work operations and training on heat illness signs and symptoms.

You cannot rely solely on the heat index to protect workers from heat stress because of the variety of factors affecting risk.


Training for prevention will help reduce the risk of heat-related injury and illness before it becomes an issue. Having a comprehensive heat illness training and prevention program that highlights the symptoms of overexposure to heat stress is important, not only for field supervision, but also for the employees whose occupation requires them to work in hot environments.

Employers, supervisors and workers need to be trained on recognizing the physiological signs and symptoms of heat-related illness; proper hydration; care and use of heat-protective clothing and equipment; effects of various risk factors affecting heat tolerance (e.g., drugs, alcohol, obesity, etc.); importance of acclimatization; importance of reporting symptoms; appropriate first aid; and procedures for contacting medical services.


The key to keeping workers safe in hot environments is staying fully hydrated, because a dehydrated person is more susceptible to show symptoms of heat illness. The National Institute for Occupational Safety and Health (NIOSH) recommends that employers provide the means for hydration and encourage their workers to hydrate themselves with potable water (between 50 and 60°F) made accessible near the work area. To maintain proper hydration it is important not to wait until becoming thirsty to drink fluids.

During short-term moderate physical exertion, 8-ounces of water every 15-20 minutes is recommended by the Centers for Disease Control and Prevention (CDC) to stay properly hydrated. The CDC advises the use of sports drinks during periods of prolonged sweating lasting two hours or longer. In these periods of more intense exertion, sports drinks can replenish and rebalance electrolytes levels. If used, the electrolyte/carbohydrate levels of sports drinks should not exceed 8% by volume.

Commonly Asked Questions
Q: What are some additional risk factors that can lead to heat stress? A: According to the CDC, workers who are at increased risk of succumbing to heat stress include those who are 65 years or older, overweight, have heart disease or high blood pressure, or take certain medications that have side effects that are triggered by extreme heat.

Q: What is the recommended sun protection factor (SPF) for sun screen for outdoor workers? A: OSHA suggests sunscreen with at least a 30 SPF or greater. Liberal amounts should be applied 30 minutes before exposure and then every two hours throughout the day.


OSHA - Heat Illness Prevention Campaign
NIOSH’s Criteria for a Recommended Standard Occupational Exposure to Heat and Hot Environments
CDC's Extreme Heat Resource Center

(Rev. 6/2017)

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Please Note:
The information contained in this publication is intended for general information purposes only and is based on information available as of the initial date of publication. No representation is made that the information or references are complete or remain current. This publication is not a substitute for review of the current applicable government regulations and standards specific to your location and business activity, and should not be construed as legal advice or opinion. Readers with specific questions should refer to the applicable standards or consult with an attorney.

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