When you think about heat as a hazard, your mind probably goes right to outdoor, environmental heat. But there are plenty of indoor work environments where heat is also a serious occupational hazard – and can even be a deadly one.
Indoor workers aren’t immune to heat exposure and heat stress. In this article, we’ll go over regulations covering indoor heat hazards, common sources of high indoor heat, and the measures employers can use to keep workers cool and safe.
US Indoor Heat Standards
Federal Indoor Heat Standards
As of February 2024, the United States does not have federal indoor heat standards specifically mandated by the Occupational Safety and Health Administration (OSHA).
However, as with other hazards not directly identified by OSHA, this does not mean that employers don’t have an obligation to provide protection from indoor heat. Under OSHA’s General Duty Clause, Section 5(a)(1) of the Occupational Safety and Health Act, all employers are required to provide a workplace that is free from recognized hazards that are likely to cause death or serious harm. While not spelled out explicitly, this includes heat-related hazards.
Although they have not created a universally accepted standard, NIOSH has come close. They have published a document outlining the criteria for a recommended standard for preventing heat stress, which includes recommendations on how to measure, control, and monitor heat stress.
State-Level Indoor Heat Standards
Some states have their own OSHA-approved state plans that cover hazards not specifically addressed by the federal OSHA standard. Below are a few states that have issued their own regulations pertaining to indoor heat.
Minnesota
Minnesota’s Rule 5205.0110 Indoor Ventilation and Temperature in Places of Employment provides some guidelines regarding exposure to high indoor temperatures, setting a maximum of two hours time-weighted average based on the physical intensity of the work being done. For example, the maximum Wet Bulb Globe Temperature (WBGT) for light work is 86ºF, while the WBGT for heavy work is 77ºF.
Oregon
Oregon’s General Occupational Health and Safety, 437-002-0156 Heat Illness Prevention standard applies to both indoor and outdoor work environments when the heat index equals or exceeds 80ºF. It provides, for example, a standard and simplified schedule for rest breaks based on the temperature of the work environment.
California
California does not currently have an indoor heat standard, but that could change soon. The Office of Administrative Law has published a notice of proposed rulemaking on Heat Illness Prevention in Indoor Places of Employment in the California Regulatory Notice Register, which initiates the formal rulemaking process. The 45-day comments period started March 31, 2023, with the legislation expected to be ratified in early 2024.
If California ratifies this proposal in the spring of 2024, California businesses will be required to implement control measures for indoor heat. When workers are present, employers will have to cool worksites below 87ºF. When workers wear PPE or are exposed to sources radiant heat, such as furnaces, businesses will need to provide a work environment below 82ºF.
Water, breaks, areas where they can cool down, cooling vests, or other means of keeping employees from overheating are proposed as alternatives if employers can’t keep the indoor environment below these specified temperatures.
Washington
The Washington State Department of Labor and Industries is currently going through a rulemaking process to update the rules for outdoor and indoor heat exposure for all industries. Employers are required to provide employees with a place to cool down and access to potable water when indoor temperatures exceed 80°F.
Sources of Indoor Heat Hazards
Indoor heat can be a significant hazard in workplaces with heat-generating processes or poor ventilation.
Common sources of indoor heat and workplaces where indoor heat can be a considerable hazard include:
- Foundries and Metal Fabrication Shops: These are perhaps the most obvious places where indoor heat can rise to dangerous levels. Welding, forging, and casting processes generate intense heat. Moreover, these processes are generally continuous, with equipment shutting down only for maintenance.
- Manufacturing Facilities: Machinery and equipment used in manufacturing processes can generate significant heat, which can lead to dangerous indoor temperatures in the absence of proper ventilation. Metalworking, plastic moulding, and glass manufacturing processes often involve high-temperature operations.
- Electrical Rooms and Boiler Rooms: These rooms are generally poorly ventilated and generate large amounts of heat.
- Kitchens, Bakeries, and Food Processing Plants: Cooking generates a lot of heat through the use of ovens, stoves, and other food processing equipment. A lack of ventilation can exacerbate the problem.
- Warehouses and Distribution Centers: Warehouses and distribution centers can become hot environments on warm days. Forklifts, conveyor systems, and other equipment can also generate additional heat. Lack of proper ventilation and a tendency for hot air to rise and become trapped can exacerbate indoor heat levels in these facilities.
- Laundries and Dry Cleaners: Industrial laundry facilities and dry cleaners can generate heat from steam presses, drying equipment, and ironing machines.
- Greenhouses and Indoor Agriculture: Plants need heat and humidity to thrive and these conditions are intentionally created to stimulate plant growth. Heaters, grow lights, and sunlight can raise temperatures to levels that can quickly induce heat-related illnesses in workers engaged in planting, harvesting, and tending to crops.
- Data Centers: Servers and computer equipment housed in data centers generate a lot of heat and typically operate around the clock. Inadequate cooling systems or improper airflow management can further elevate temperatures in these facilities, posing risks to workers responsible for maintaining and operating the equipment.
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Control Measures for Indoor Heat
In workplaces where indoor heat can rise to hazardous levels, several control measures should be implemented to mitigate the risks of heat-related illnesses.
Here are some of the most important ones.
Engineering Controls
- Proper Ventilation: Ensure adequate systems are in place to remove heat and humidity from indoor work areas. Mechanical and natural ventilation are the most common cooling systems in indoor non-office environments. While most of us would prefer air conditioning, this is not always feasible.
- Insulation: The same insulation that keeps the building warm in the winter will help insulate it from extreme heat in the summer. If the heat is environmental and not related to work processes, good insulation will help keep the building cool. But keep in mind that if the heat is produced indoors, insulation might make things worse by preventing the heat from dissipating.
- Heat-Reducing Equipment: Implement heat-reducing equipment or processes where feasible, such as cooling fans, heat shields, and heat-resistant materials.
- Shading: Provide shading to reduce direct sunlight exposure to indoor areas with large windows or skylights.
Administrative Controls
- Workplace Design: Where possible, design work processes and schedules to minimize exposure to high temperatures. For example, schedule strenuous tasks during cooler times of the day or plan a project for the cooler season of the year.
- Work/Rest Cycles: Overheating happens when heat surpasses the body’s ability to cool itself. To prevent this from happening, provide cool rest areas and mandate employees to take regular breaks and rest in these areas.
- Hydration Programs: All workers working in hot indoor environments should have access to cool water. Depending on the acclimation, temperature, and work intensity, electrolyte drinks might also be recommended. Implement a hydration program and encourage frequent hydration.
- Training and Education: Workers should be able to recognize the signs and symptoms of heat-related illnesses, in themselves and in co-workers, as well as preventive measures and emergency procedures. Training should be provided to all new employees, along with refreshers if the hot working environment is seasonal.
- Emergency Response: Training should also include protocols for responding to heat-related emergencies, including procedures for removing affected workers from hot environments, providing first aid, and seeking medical assistance when necessary.
Personal Protective Equipment (PPE)
- Cooling PPE: Provide workers with cooling vests, cooling hats, or other personal cooling devices to help regulate body temperature.
- Protective Clothing: If no specific PPE is mandated, ensures that workers wear lightweight, breathable clothing appropriate for the work environment to minimize heat retention. If PPE is required, it should be selected to meet the criteria listed above.
Monitoring and Surveillance
Regularly monitor temperatures in hot work areas using thermometers. Use heat stress monitoring systems to identify areas of concern or when temperatures rise above specific thresholds.
Where possible, the temperature monitoring should be connected to cooling and ventilation systems, so that the temperature is automatically regulated to acceptable parameters.
Summary
Despite the lack of specific regulations, employers are obligated under the OSHA General Duty Clause to ensure workplaces are free from recognized hazards, including heat-related risks. While some states like Minnesota and Oregon have established their standards, others like California are in still the process of developing regulations.
Where indoor heat is an occupational hazard, it’s important to ensure that adequate controls are in place to protect workers from heat illnesses. Controls are variable and, depending on the specifics of the work environment, could include ventilation, scheduling, hydration, and cooling PPE.
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