Audit, Compliance and Risk Blog

Preventing Work-related Heat Illness

Posted by Jon Elliott on Tue, Jun 29, 2021


Summer has arrived, bringing record-breaking heat to parts of North America. It's time to remember that outdoor work in the summer sun can lead to heat illness, as can indoor work in spaces that aren’t sufficiently insulated or cooled.

In the United States, the federal Occupational Safety and Health Administration (OSHA) and most state OSH programs provide guidance to employers and their workers. California's Division of Occupational Safety and Health (Cal/OSHA) administers detailed regulatory requirements for outdoor first promulgated in 2005, and Washington has enforced state-level rules since 2007. Canadian occupational health and safety agencies also recognize “thermal stress” as a workplace hazard, with attention to both heat and cold. California has been working on standards for indoor workplaces since 2017.

If you have outdoor workers in California you must comply with the following requirements, while if you're anywhere else you should at least consider them. 

How Does Heat Cause Illness?

When someone works in a hot environment, their body must shed excess heat to maintain a stable internal temperature. This is accomplished mainly by circulating blood to the skin, and by sweating. This becomes less effective when the air temperature is close to or warmer than normal body temperature, and/or when the humidity is high enough to prevent effective evaporation. Even when it works, the worker’s body tends to heat up, and fluids and salts lost by sweating will have to be replaced.

Definitions of "heat illness" vary, but California’s is typical: "a serious medical condition resulting from the body's inability to cope with a particular heat load, and includes heat cramps, heat exhaustion, heat syncope and heat stroke." Recognizing that each individual’s body may respond differently to workplace conditions, professionals and regulators provide different guidance about conditions that should trigger explicit attention to the hazard, including

  • California’s outdoor heat illness standard focuses on agriculture, construction, landscaping, oil and gas extraction and transportation. It requires employers to provide adequate access to water and shade when outdoor temperature exceeds 80 oF, or are at least 10 oF higher than the average of the preceding 5 days.

  • Washington sets a threshold of 89 oF for most situations, but reduces that to 77 oF if workers are wearing “double-layer woven clothes including coveralls, jackets and sweatshirts”, and to 52 oF for those wearing “nonbreathing clothes including vapor barrier clothing or PPE such as chemical resistant suits.”

  • to adjust for humidity, relative humidity is important. As an example, the US National Weather Service presents a Heat index that reflects both temperature and humidity.

How Do I Prevent Heat Illness, And Address It If It Occurs?

Heat illness can be prevented if workers have the chance to keep their body temperatures down, to cool off if they start to overheat, and to rehydrate. Cal/OSHA requires California employers to take these four steps to prevent heat illness from outdoor work:

  • Employee training. Provide (and document) effective training to each employee before beginning work that should reasonably be anticipated to result in exposure to the risk of heat illness; provide additional implementation training to supervisors. Training must cover:

    • Environmental and personal risk factors for heat illness, the added burden of heat load caused by exertion, clothing, and personal protective equipment.

    • Employer procedures for complying with the requirements of this standard.

    • Importance of frequent consumption of small quantities of water, up to 4 cups per hour, when the work environment is hot.

    • Importance of acclimatization.

    • Different types of heat illness and the common signs and symptoms of heat illness.

    • Importance of immediate reporting to the employer, directly or through the employee's supervisor, symptoms or signs of heat illness in themselves, or in co-workers.

    • Employer's procedures for responding to symptoms of possible heat illness, including emergency medical services if necessary.

    • Employer's procedures for contacting emergency medical services, and if necessary, for transporting employees to a point reachable by emergency medical services.

    • Employer's procedures for ensuring that, in an emergency, clear and precise directions to the work site can and will be provided as needed to emergency responders. These must include designating a person to ensure that emergency procedures are invoked when appropriate.

    • Water. Provide enough fresh potable water so each employee can drink at least 1 quart per hour, and encourage them to do so.

  • Shade. Cal/OSHA requires employers to make shade that “substantially blocks direct sunlight” available when it’s at least 80 oF in an outdoor workplace

    • either open to the air or provided with ventilation or colling

    • at least enough to accommodate employees during rest or recovery periods, or eating periods onsite, with enough space to let them sit normally without physical contact with each other

    • “as close as practicable” to work areas

  • Cool-down rest periods. Employees must be allowed and encouraged to take a cool-down rest in the shade for at least 5 minutes when they feel the need to do so to protect themselves from overheating. The employer must allow access to shade at all times.

  • Heat Illness Prevention Plan. Employers must develop and implement written procedures for complying with these requirements, including the items above plus:

    • High-heat procedures when the temperature equals or exceeds 95 oF. These procedures shall include the following to the extent practicable:

- emergency response procedures

- acclimatization methods and procedures.

California’s latest proposal for indoor workplaces outlines similar requirements, with the following adjustments:

  • The proposal would apply when the heat index is above 87 oF, or above 82 oF when employees work in the presence of radiant heat or wear clothing (including PPE) that restricts heat removal

  • Rather than shade, the proposal provides a more general requirement for a “cool-down area”

Now what?

Employers outside California are not bound by these requirements, but should consider them as guidelines for use in evaluating whether suitable water, shade, training and procedures are available to address heat hazards, if any.

Self-Assessment Checklist

Do any of my organization's workers work in situations where ambient heat may create a hazard of heat illness:

  • Outdoors (e.g., agricultural or construction work)?

  • Indoors (e.g., work in manufacturing or other processes involving hot materials or equipment)?

If so, does the organization provide appropriate:

  • Training (tailored to the workplace source(s) of heat hazards, preventive measures, and responses to heat illness?

  • Water?

  • Shade or other appropriate ways for workers to cool down?

  • Planning and procedures?

Where Can I Go For More Information?

- Cal/OSHA “Heat Illness Prevention webpage

- California Occupational Safety and Health Standards Board “Heat Illness Prevention in Indoor Places of Employment” working group webpage 

- Employment and Social Development Canada “Thermal stress in the work place” 

- Canadian Centre for Occupational Health and Safety “Hot Environments - Health Effects and First Aid” webpage

Like What You've Read? Subscribe to Our Blog Now

About the Author

Jon Elliott is President of Touchstone Environmental and has been a major contributor to STP’s product range for over 30 years. 

Mr. Elliott has a diverse educational background. In addition to his Juris Doctor (University of California, Boalt Hall School of Law, 1981), he holds a Master of Public Policy (Goldman School of Public Policy [GSPP], UC Berkeley, 1980), and a Bachelor of Science in Mechanical Engineering (Princeton University, 1977).

Mr. Elliott is active in professional and community organizations. In addition, he is a past chairman of the Board of Directors of the GSPP Alumni Association, and past member of the Executive Committee of the State Bar of California's Environmental Law Section (including past chair of its Legislative Committee).

You may contact Mr. Elliott directly at:

Tags: EPA, CalEPA, Canada, Heat Wave, Heat