Protecting Workers In Hot Environments

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Exposure to excessive heat on the job, both indoors and outdoors, is a recognized hazard faced by many American workers. Occupational heat stress is the combination of metabolic heat[1], environmental factors (e.g., temperature, humidity), and the type of clothing worn. Many materials, especially impermeable materials used in personal protective equipment (PPE), can trap heat close to the skin and limit or prevent natural cooling such as through sweat evaporation. These factors together can lead to additional heat affecting the body, increasing core body temperature, and putting workers at risk for heat-related illnesses and injuries. These heat-related illnesses and injuries may lead to serious health conditions, disability, or death.

To understand the full impact of heat in the workplace, it is very important to document both its direct and indirect effects. Workers should not be blamed or disciplined for incidents where heat was a significant contributing factor.

This fact sheet discusses heat stress, how it can impact your health and safety at work, how heat-related illnesses can be prevented, and strategies your employer, as well as Teamster members and local unions, can use to address these hazards and minimize your risk of exposure. 

What Causes Heat Stress?

Hazardous heat exposure can occur indoors or outdoors and can occur during any season if the conditions are right, not only during heat waves. Below are seven (7) risk factors which may lead to heat illness: 

  1. High temperature and humidity, direct sun exposure, no breeze or wind.
  2. Heavy physical labor, indoors or outdoors.
  3. Not drinking enough water, dehydrated.
  4. Waterproof clothing or personal protective equipment (PPE) that are not breathable and prevent or slow the body’s ability to lose excess heat.
  1. Not being physically conditioned/adjusted (acclimated) to a hot workplace. Acclimatization is the natural process where the body adjusts to a change in its environment over a short period of time through steady and gradual exposure.
  2. Personal characteristics such as age, physical fitness, degree of acclimatization, metabolism, dehydration, use of drugs, alcohol or certain medications, and a variety of medical conditions, such as hypertension, all affect a person’s sensitivity to heat.

Approximately 50% to 70% of heat related fatalities in outdoor work environments occur in the first few days on the job. This number can be substantially reduced if workers are provided with the opportunity to build a tolerance gradually, a process called heat acclimatization. Lack of acclimatization represents a major risk factor for fatal outcomes.

What Disorders can be Caused by Repeated Exposure to High Heat Environments?

High heat exposure can aggravate existing health conditions such as asthma and heart disease and even increase a person’s vulnerability to environmental toxins (e.g., chemicals/pesticides). Repetitive heat stress can also cause depressed kidney function and lead to chronic kidney disease. 

The table below presents several heat related illnesses, their signs and symptoms: 

Heat-Related IllnessSymptoms and Signs
 Heat stroke·      Confusion·      Slurred speech·      Unconsciousness·      Seizures·      Heavy sweating or hot, dry skin·      Very high body temperature·      Rapid heart rate
 Heat exhaustion·      Fatigue·      Irritability·      Thirst·      Nausea or vomiting·      Dizziness or lightheadedness·      Heavy sweating·      Elevated body temperature or fast heart rate
 Heat cramps·      Muscle spasms or pain·      Usually in legs, arms, or trunk
 Heat syncope·      Fainting·      Dizziness
 Heat rash·      Clusters of red bumps on skin·      Often appears on neck, upper chest, and skin folds
 Rhabdomyolysis (muscle breakdown)·      Muscle pain·      Dark urine or reduced urine output·      Weakness

How Can Heat-related Illnesses be Prevented? 

Most heat‑related health problems can be prevented or reduced with your employers’ commitment to conducting a risk assessment and providing the most protective hazard controls.  Your employer should develop a written heat-related illness prevention program and designate a responsible person to oversee the program. Below are key elements of a heat-related illness prevention program:

Engineering Controls

A variety of engineering controls can reduce workers’ risk of heat related injuries/illnesses:

Administrative or Work Practice Controls

Some worksites cannot be cooled by engineering controls or by those controls alone. In addition to engineering controls, employers should modify work practices (also known as ‘administrative controls’) when heat stress is too high to work safely:

total body cooling, IV fluids, etc.  Administer appropriate first aid to any worker who is developing a heat-related illness.

Personal Protective Equipment (PPE)

In most cases, heat-related illnesses should be reduced by engineering controls or work practice modifications. However, where heat stress levels exceed recommended limits, there are types of PPE that can be worn to protect against heat exposures both when actively engaged at work and at rest[2]. These are called auxiliary cooling systems or personal cooling systems (e.g., water-cooled garments, air-cooled garments, cooling vests, and wetted overgarments) and can range in simplicity, cost, and maintenance.

Wearable personal cooling systems, however, have limitations such as:

Are There Any Federal and State Standards that Cover Heat-related Illnesses?

The federal Occupational Safety and Health (OSHA) Administration does not have a standard addressing the hazards of heat exposure. The federal OSHA office in Region 6 (covering private sector workers in Arkansas, Louisiana, Oklahoma, Texas and New Mexico) has a ‘Regional Emphasis Program’ (REP) that  conducts inspections for outdoor heat-related health hazards when the high temperature is forecast to be above 80°F.[3]Pressure from worker advocate groups, environmental organizations, and unions, including the IBT, has resulted in Congressional legislation, the ‘Asunción Valdivia Heat Illness and Fatality Prevention Act,’ that if passed would require OSHA to create a new enforceable standard to protect both indoor and outdoor workers exposed to extreme temperatures. 

OSHA can, however, respond to heat related complaints by enforcing the following:

OSHA also has an educational ‘Campaign to Prevent Heat Illness’ and provides helpful information on its Occupational Exposure to Heat webpage[4]. (

On the state level, California, Washington, Oregon, and Minnesota, have issued heat protection standards of their own. Protections in Oregon’s emergency standard, which is the most protective of them all, apply to both indoor and outdoor employees.  The Oregon standard is triggered when the ‘heat index’ equals or exceeds 80 degrees Fahrenheit. The heat index is commonly known as the ‘feels like temperature’ and considers both temperature and relative humidity in its calculation. Fortunately, the heat regulations in both Oregon and Washington apply to vehicle cab environments that are not managed by fans or air conditioning. 

Maryland and Virginia are also in the process of developing heat illness prevention standards. 

What Can Teamster Members and Local Unions Do to Help Protect Members from Heat-related Illnesses?

Currently, the IBT Safety and Health Department offers training on heat stress through modules in the following courses:

Please refer to the IBT Safety and Health Department website,, for more information and resources and feel free to contact us at 202-624-6960.

More Information [ED1] [MK2] 

Heat – Overview: Working in Outdoor and Indoor Heat Environments | Occupational Safety and Health Administration

Heat Stress Guide | Occupational Safety and Health Administration (

OSHA-NIOSH Heat Safety Tool App 

Heat Stress | NIOSH | CDC

Occupational Exposure to Heat and Hot Environments | NIOSH | CDC

California Code of Regulations, Title 8, section 3395. Heat Illness Prevention in Outdoor Places of Employment

DOSH – Heat related illness prevention and information (

Oregon OSHA Heat Illness Prevention Rule Questions and Answers

Oregon Occupational Safety and Health: Heat stress: State of Oregon

Washington State Emergency Heat Exposure Rule for Outdoor Workers

Heat Exposure Educational Information

MN OSHA Heat Stress Guide

MN OSHA Compliance: Heat stress | Minnesota Department of Labor and Industry

[1] Metabolic heat is the heat your body creates naturally which can increase during exercise or physical exertion from work.

[2] Limiting Heat Burden While Wearing Personal Protective Equipment (PPE)

[3] Regional Emphasis Program for Heat Illnesses (

[4] Heat – Overview: Working in Outdoor and Indoor Heat Environments | Occupational Safety and Health Administration

 [ED1]are these meant to be website links?  if so the webaddresses are not provided here besides

 [MK2]links established