Whether it occurs indoors or outside, heat stress poses a serious risk on the job. According to the Centers for Disease Control and Prevention, heat stress causes medical problems such as heat stroke, heat exhaustion, heat cramps and heat rash. It may also lead to work-related injuries caused by fogged-up safety goggles, sweaty palms, burns due to accidental contact with hot surfaces and dizziness. California was the first state to implement regulations to prevent heat stress on the job.


In September 2006, the California State Occupation Safety and Health Administration (Cal/OSHA) implemented a Heat Illness Prevention Program. Initially directed at agricultural, construction and other outdoor workplaces, the regulations also apply to indoor work settings where heat exposure may be a problem, such as foundries, factories, warehouses without air conditioning and commercial kitchens. They also cover workers who must wear protective clothing or gear that can increase body temperature.

Daytime temperatures in California can range from more than 60 degrees Fahrenheit to more than 100 degrees, and many older buildings do not have central air conditioning. For example, on a hot summer day in 2009, the City of Oakland Public Library closed four branches because they did not have air conditioning and the indoor temperature reached 86 degrees.

California Regulations

Four sections of Title 8 of the California Code of Regulations cover standards for indoor heat exposure. Section 3203 requires that employers take the steps necessary to protect employees’ health and safety when the temperature exceeds 85 degrees in the workplace. Section 3395 gives step-by-step instructions for implementing the heat illness prevention program. Section 3363 requires that workers have a regular supply of fresh drinking water, and Section 3400 requires medical services and first aid for workers exposed to excessive heat.

Basic Program Requirements

The Cal/OSHA Heat Illness Prevention Program requires that employers take four basic steps to prevent illness. First, all employees and managers must receive training in heat illness symptoms, treatment and prevention. Second, the employer must provide enough fresh drinking water so that each worker at risk for heat illness can drink one quart of water each hour. Managers must encourage their workers to drink water throughout the day to prevent illnesses. Third, when working indoors, employees exposed to heat must be given a cooler or air-conditioned area away from the heat to take regular rest breaks. Finally, employers must develop and implement written standards for heat illness prevention, including worksite evaluations, corrective actions and employee communications.

Additional Requirements

Employers must take additional steps to prevent heat illness. They must provide opportunities for employee acclimatization, which gradually increases the time during which an employee can be exposed to high temperatures. Acclimatization can take several days and may involve more frequent rest breaks or having the person work in the high heat area for only part of the day.

Businesses may also need to adjust work schedules in buildings with no air conditioning so that employees work in the early morning or evening, when it is cooler. Employers are required to be prepared for medical emergencies, including having written emergency procedures and accessible first aid kits on site and working with emergency medical services.