California Indoor Heat Regulation: Triggers, Breaks, and Penalties

California’s indoor heat regulation, codified at Title 8, Section 3396 of the California Code of Regulations, requires employers to protect workers from heat illness in any indoor workspace that reaches 82 degrees Fahrenheit or higher. The rule took effect in July 2024 and layers specific duties — water, cool-down areas, rest breaks, a written plan, training, and temperature monitoring — on top of every employer’s existing obligation to identify and correct workplace hazards.¹ Cal/OSHA enforces it, and the penalties for ignoring it reach six figures.

Which Workplaces Are Covered

The standard applies to all indoor work areas where the temperature equals or exceeds 82°F while employees are present. Warehouses, manufacturing floors, restaurant kitchens, and laundry facilities are typical examples, but any enclosed indoor space that gets that hot is covered. The regulation defines “indoor” as a space under a ceiling or overhead covering that is enclosed along its perimeter by walls, doors, or other physical barriers.¹

A few situations fall outside the rule. Employees teleworking from a location of their own choosing that is not under the employer’s control are exempt. Brief exposures of less than 15 minutes in any 60-minute period are exempt when the temperature stays between 82 and 95 degrees, though this carve-out does not apply to vehicles without working air conditioning or to shipping and intermodal containers during loading and unloading. Emergency operations directly involved in protecting life or property are exempt. So are state prisons operated by the California Department of Corrections and Rehabilitation, local detention facilities, and local-government-operated juvenile facilities. The exemptions are narrow; if your workplace does not clearly fit one of them, the standard applies.

Even below 82°F, every California employer still has to identify and correct heat as a hazard under the Injury and Illness Prevention Program requirement in Section 3203.² The indoor heat standard adds more specific duties once the thermometer crosses the trigger.

The Two Temperature Triggers

Two numbers do most of the work in this regulation.

At 82°F, the baseline obligations kick in. Once the temperature or heat index reaches this level, the employer must provide drinking water, access to a cool-down area, observation for signs of heat illness, and the other general provisions of the standard.

At 87°F, employers must use feasible engineering controls to bring the temperature or heat index back below that mark. Whichever reading is higher (temperature or heat index) is the one that counts.

A stricter version of the second trigger applies to workers near furnaces, ovens, or other intense radiant heat sources, and to workers wearing clothing that traps heat, such as chemical-resistant suits or heavy personal protective equipment. For them, engineering controls must aim to bring conditions below 82°F, not 87°F.¹

Water, Cool-Down Areas, and Rest Breaks

Drinking water must be fresh, suitably cool, free of charge, and located close to both the work area and the cool-down area. A single water cooler at the far end of a warehouse is not compliance.

Employers must provide a cool-down area kept below 82°F, unless doing so is infeasible. The area has to be as close as practical to where employees are working and shielded from direct sunlight and high-radiant-heat sources.

Workers are entitled to preventive cool-down rest periods whenever they feel the need. A supervisor cannot order someone back to work until any symptoms of heat illness have resolved, and the break must last at least five minutes beyond the time it takes to reach the cool-down area. Five minutes is the floor. If symptoms persist, the worker stays off the job.¹

Written Plan and Controls

Every covered employer must maintain a written Indoor Heat Illness Prevention Plan. The plan has to explain how the employer will supply water, cool-down areas, rest breaks, acclimatization observation, training, and emergency response.

Engineering controls come first: air conditioning, improved ventilation, fans to increase air movement, shielding from radiant heat sources, or other physical changes to the environment. The goal is to pull the temperature or heat index below the applicable threshold.

When engineering controls alone cannot do it, administrative controls fill the gap. Those include adjusting schedules to avoid peak heat, rotating workers between hot and cooler tasks, slowing the pace of work, and adding rest breaks. In warehousing, food manufacturing, and similar industries, most employers end up relying on a combination of both.

Temperature Monitoring and Recordkeeping

Employers must measure and record the temperature or heat index (whichever is higher) whenever the applicable trigger is reached. Measurements have to be taken in the immediate area where employees work, not in a cooler office down the hall.

The regulation accepts a thermometer shielded from radiant heat sources or equipment that produces results consistent with the National Weather Service heat index chart in Appendix A. Initial readings should be taken when there is reason to believe the trigger has been crossed, and new readings are required whenever conditions are expected to rise 10 degrees or more above the previous measurement.

Records of each measurement — including date, time, and specific location — must be kept for at least 12 months or until the next set of measurements is taken, whichever is later. These records have to be available to employees and Cal/OSHA representatives on request.¹

Training, Supervisors, and Acclimatization

Every employee who could be exposed to indoor heat needs effective training, meaning training delivered in a language and manner the employee actually understands. The required topics include the signs and symptoms of heat illness (from heat rash and cramps through heat exhaustion and heat stroke), how to respond to a heat emergency, how to call 911 and give clear directions to the worksite, the employer’s procedures for water and cool-down areas, and the worker’s right to take preventive cool-down breaks and report hazards without retaliation.

Supervisors must get all of that training plus additional instruction on implementing the standard, recognizing and responding to a worker in trouble, and activating emergency procedures. Before overseeing any work that could involve heat exposure, a supervisor needs this training in hand.

Acclimatization gets its own rules. New employees and workers returning after an absence of 14 or more days have to be closely observed during their first 14 days on hot work. The body adapts to heat gradually, with most people reaching peak acclimatization within four to fourteen days of regular exposure for at least two hours a day. During that window, workers are more vulnerable, and supervisors are expected to watch for warning signs more actively.¹

Emergency Response and Reporting

The written plan must spell out emergency response procedures. At a minimum, the employer has to be able to provide first aid, contact emergency medical services immediately for severe symptoms such as confusion, loss of consciousness, or slurred speech, and make sure responders can find the worksite. Someone should always stay with an affected worker, because heat illness can escalate from manageable to life-threatening in a short time.

If a heat-related incident causes a serious injury, hospitalization for more than 24 hours, or death, the employer must report it to Cal/OSHA immediately by phone or through Cal/OSHA’s online reporting system. Failing to make that report carries a civil penalty of at least $5,000.³

Filing a Complaint and Protection From Retaliation

If your employer is not following the rule, you can file a complaint with the Cal/OSHA Enforcement District Office nearest your worksite. Complaints are accepted by phone during business hours (Monday through Friday, 8 a.m. to 5 p.m.) or by email, and Cal/OSHA’s zip code locator will point you to the right office. Your identity is kept confidential unless you ask otherwise.⁴

It is illegal for an employer to fire, demote, suspend, or otherwise retaliate against a worker for reporting unsafe conditions, filing a Cal/OSHA complaint, or taking part in a safety proceeding. A worker who is retaliated against is entitled to reinstatement and reimbursement of lost wages and benefits, and an employer who willfully refuses to reinstate a worker found eligible through a hearing or grievance commits a misdemeanor.⁵

Penalties for Violations

Cal/OSHA updates its civil penalty figures each year. As of the amounts effective January 1, 2025, the maximums are:⁶

Serious violation: up to $25,000 per violation.
General or regulatory violation, including recordkeeping failures: up to $16,285 per violation.
Willful or repeat violation: up to $162,851, with a minimum of $11,632 for willful violations.

These add up quickly. An employer missing the written plan, the monitoring records, the cool-down area, and the training can be cited on each count separately. Willful violations, where Cal/OSHA finds the employer knew about the hazard and ignored it, draw the steepest fines.

1
Department of Industrial Relations. California Code of Regulations Title 8 Section 3396 – Heat Illness Prevention in Indoor Places of Employment
2
Department of Industrial Relations. California Code of Regulations Title 8 Section 3203 – Injury and Illness Prevention Program
3
California Legislative Information. California Labor Code Section 6409.1
4
Department of Industrial Relations. File a Complaint with Cal/OSHA
5
California Legislative Information. California Labor Code Section 6310
6
California Department of Industrial Relations. Cal/OSHA Increases Civil Penalty Amounts for 2025