With exceptions, the new Cal OSHA heat stress law applies to all indoor work areas where the temperature equals or exceeds 82°F when workers are present. It does not apply to outdoor working conditions that fall under the scope and application of California Code of Regulations title 8, section 3395.

The indoor heat safety standard does not apply to:

• Workplaces where employees are teleworking and the location is not under the control of the employer.
• Prisons, juvenile, and local detention facilities.
• Emergency operations that are directly involved in the protection of life or property.
• Incidental heat exposures above 82°F but less than 95°F for less than 15 minutes per hour.

These exceptions do not apply to:

• Vehicles without effective and functioning air conditioning.
• Shipping or intermodal containers during loading, unloading, or related work.

With soaring temperatures making 2024 one of the hottest years on record, California has expanded worker protections beyond outdoor environments. The new Cal/OSHA indoor heat stress mandate addresses the urgent need to safeguard employees in indoor workplaces from life-threatening heat hazards.

By mandating cool-down areas in workplaces exceeding 82°F, this regulation takes a crucial step towards preventing heat-related illnesses.

Cal/OSHA is the California state division of the Occupational Safety and Health Administration. It was established in 1973 and is part of the Department of Industrial Relations.

It is responsible for enforcing workplace safety and health regulations and providing workers and employers with the assistance they need to adhere to the occupational safety guidelines.

The Cal/OSHA indoor heat safety regulations share many similarities with the outdoor heat stress regulations. Many of the same precautions as outdoor environments apply to indoor settings, but there are subtle differences that set them apart:

Temperature Thresholds:

• Outdoor: Focuses primarily on air temperature, with specific thresholds for different levels of exertion.
• Indoor: Uses a combination of air temperature and heat index, with lower trigger points for indoor environments.

Work Environment:

• Outdoor: Emphasizes shade, hydration, and rest breaks in outdoor settings.
• Indoor: Focuses on ventilation, air conditioning, and engineering controls to cool down the work environment.
• NOTE: An indoor workplace’s internal temperature can also be impacted by factors such as levels of insulation and reflective shields.

Clothing and Equipment:

• Outdoor: Often requires specific heat-protective clothing and equipment for outdoor workers.
• Indoor: Addresses the impact of restrictive clothing on heat stress and requires employers to provide suitable attire.

Acclimatization:

• Both regulations include provisions for acclimatizing workers to hot conditions. However, specific requirements and timelines may vary.

Monitoring and Recordkeeping:

• Outdoor: Requires extensive monitoring of weather conditions and worker hydration.

Indoor: Emphasizes temperature monitoring and recordkeeping to identify and address heat hazards.

A cool-down area is a shaded indoor or outdoor space with good ventilation or air conditioning. It should be below 82°F when possible.

Employers must provide at least one cool-down area on site and encourage employees to take cool-down breaks as needed, with breaks lasting at least 5 minutes to prevent indoor heat stress.

Employers may be covered under both the indoor and outdoor regulations if they have both indoor and outdoor workplaces.

• Potable drinking water must be made available at all times and at no cost to workers. 
• Workers should be encouraged throughout their work shifts to drink water. 
• Cal/OSHA recommends visually examining, tasting the water, and pouring some on the skin to ensure that the water is fresh, pure, and cool. 
• The water must also be located in a readily accessible place to all workers.
• Water must be placed strategically to encourage workers to drink adequate amounts. For instance, in a large warehouse, water should be placed throughout the entire building and workspace area.

Employees are required to provide employees with a cool place for rest breaks once the indoor temperature hits 82°F.

OSHA recommends the use of wet bulb globe temperature (WBGT) monitors to measure workplace environmental heat. The WBGT can be adjusted to address indoor heat stress or outdoor conditions as required. WBGT has continued to be widely used as it’s a convenient, efficient, and accurate measure of heat stress and real-world conditions.

The wet bulb globe temperature (WBGT) can be measured using on-site weather stations, handheld WBGT monitors, or online WBGT and weather monitoring apps. These WBGT monitors can either be handheld or part of a weather station and measure temperature, humidity, sunlight, and other factors to calculate the WBGT index.

The heat index is a measurement that shows how hot the human body feels outside when relative humidity and air temperature are combined. It is calculated for shaded areas and doesn’t account for direct sunlight, physical activity, or wind. 

Different people may also perceive heat differently due to factors like hydration, body shape, and metabolism. The scale spans from a low of 80°F and 40% humidity (Caution) to a high of 110°F and 100% humidity (Extreme Danger).

Learn more about the heat index here.

Several elements contribute to occupational indoor heat stress, including:

• Environmental conditions (temperature, humidity, sunlight, airflow) 
• Heat sources in the workplace 
• Intensity of physical exertion 
• Protective gear
• individual factors like overall health