The California Heat Illness Standards, Indoor and Outdoor, Explained

California runs two heat illness standards, not one. 8 CCR 3395 covers outdoor places of employment and has been in force for years. 8 CCR 3396 covers indoor places of employment and took effect on 23 July 2024. They have different triggers, different duties and different written plan contents, and an employer with both kinds of exposure needs both sets of procedures.

Federal OSHA has no heat standard at all. It enforces heat under the General Duty Clause, backed by a National Emphasis Program that took effect on 10 April 2026, while a proposed rule sits unfinished.

What follows answers the questions Cal/OSHA and federal OSHA actually publish, in the words they are asked, with the citation and the number in the first sentence of every answer. Every figure on this page was checked against the regulation text on 20 August 2026. Where a threshold is commonly misreported, this page says what the misreport is.

The five numbers that decide almost everything

Most heat compliance failures trace to a wrong number rather than a missing program. These are the ones that matter, and three of the five are routinely quoted incorrectly.

Threshold	What attaches	Citation
No temperature	Outdoor water, training, emergency response, written plan, shade on request	8 CCR 3395
80°F outdoors	Shade must be present, not merely available on request	8 CCR 3395
95°F outdoors	High-heat procedures, for five named industries only	8 CCR 3395
82°F indoors	Water, cool-down area, training, emergency response, written plan	8 CCR 3396
87°F indoors	Control measures: engineering, then administrative, then personal heat-protective equipment	8 CCR 3396

The 82 degree indoor figure also applies at 87's place in two situations: where employees wear clothing that restricts heat removal, and where they work in a high radiant heat area. In both of those the control measures start at 82 rather than 87.

Indoor is the one most employers have not addressed

8 CCR 3396 is recent, and the definition of indoor is broader than the word suggests. The standard defines an indoor place of employment as a space under a ceiling or overhead covering that restricts airflow and enclosed along its entire perimeter by walls, doors, windows, dividers, or other physical barriers that restrict airflow, whether open or closed.

Whether open or closed is the operative phrase. A warehouse with every dock door rolled up is indoors. So is a fabrication shop, a mechanical room, a parking structure level, an unconditioned equipment closet, a garage with the door down, and a residential attic. Employers who read the headline as a factory rule are usually running uncovered exposure across a large part of the operation.

For contractors servicing equipment inside those spaces, the indoor standard stacks on top of the confined space question, and both can apply on the same job. That combination is worked through on our page for residential HVAC contractors.

Where the written plan usually falls down

Both standards require a written Heat Illness Prevention Plan in English and in the language understood by the majority of the employees, kept at the worksite. The failure pattern is consistent and it is not usually the absence of a document.

• The plan predates July 2024. Anything written before then addresses 3395 only. The indoor standard is not in it.
• The plan restates the regulation. Both standards require the employer's own procedures. Copying the rule back is not a procedure. Where is the water, who refills it, where is the shade, who watches the new hire, who calls 911 and from which phone.
• No measurement records. The indoor standard requires dated, timed, location-specific measurements retained for 12 months or until the next set, whichever is later. Most employers have none.
• No cool-down area answer for mobile work. A crew on a customer's property has no break room. That has to be answered in writing before the day it is needed.
• Translation missing. The majority language requirement is explicit in both sections and it is a fast citation.

We write and audit these plans. Consulting covers the written program, training covers the employee and supervisor curricula both standards require, and Fractional EHS covers the companies that need someone owning it month to month rather than once a year.

What we do not sell for heat, and why that is worth saying

We stock no heat control products. Not cooling vests, not misting equipment, not shade canopies, not heat index meters. Everything on this page is written from the standards and from running these programs, and there is no product at the end of it.

That matters for one specific answer. The control measure hierarchy in 8 CCR 3396 puts personal heat-protective equipment last, after engineering controls and after administrative controls. A vendor whose business is cooling vests has a reason to skip to the third step. We do not, so the advice here is the order the standard actually sets.

California and federal heat questions, answered

Where and when does the outdoor heat standard apply?

8 CCR 3395 applies to all outdoor places of employment in California, with no temperature floor for the core duties. Water, access to shade on request, training, emergency response and a written plan are owed whenever people work outdoors, not only when it is hot. Certain obligations then switch on at specific temperatures: shade must be present above 80 degrees Fahrenheit, and high-heat procedures start at 95 degrees for five named industries. The section is formally titled the Maria Isabel Vasquez Jimenez heat illness standard.

What is considered sufficient access to drinking water?

One quart per employee per hour for the entire shift, under 8 CCR 3395. The water must be potable, fresh, pure, suitably cool, provided free of charge, and located as close as practicable to where the crew is working. The quantity is the part people get wrong. A quart an hour across an eight hour shift is two gallons per person per day, which is a supply problem on a jobsite with no running water, not a signage problem. The employer must also encourage frequent drinking of small amounts, and the training standard puts a figure on it: up to four cups per hour.

At what temperature is shade required?

Above 80 degrees Fahrenheit, under 8 CCR 3395. When the outdoor temperature exceeds 80 degrees the employer must have shade present and open to employees. At or below 80 degrees the employer either provides that same shade or provides timely access to shade on an employee's request. Note the second half. Below 80 degrees the duty does not disappear, it converts into an on-request duty, and a crew that has nowhere to go when someone asks is still out of compliance.

What is considered sufficient access to shade?

Enough shade to seat everyone on a recovery or rest period at once, under 8 CCR 3395. The standard is explicit about the geometry: employees must be able to sit in a normal posture fully in the shade without having to be in physical contact with each other. Shade also has to be as close as practicable to the work. A single pop-up canopy for a twenty person crew does not satisfy this, and neither does shade a five minute walk away.

Does a vehicle count as shade?

Only if it is running with air conditioning. 8 CCR 3395 defines shade as blockage of direct sunlight and then says so directly: a car sitting in the sun does not provide acceptable shade to a person inside it unless the car is running with air conditioning. This is the single most common field substitution and it fails on inspection. A truck cab with the windows down is not shade.

What are high-heat procedures and what industries are required to comply?

High-heat procedures start at 95 degrees Fahrenheit and apply to five named industries under 8 CCR 3395: agriculture, construction, landscaping, oil and gas extraction, and transportation or delivery of agricultural products, construction materials or other heavy materials. The transportation category excludes operating an air-conditioned vehicle where there is no loading or unloading. The procedures require effective communication, observing employees for signs of heat illness, designating who is authorized to call emergency services, reminding workers to drink water, and holding a pre-shift meeting on the high-heat procedures. Agriculture carries one more: a mandatory ten minute cool-down rest every two hours above 95 degrees. Almost nothing published on the internet names the five industries correctly, and if you are not on the list the 95 degree procedures do not attach to you.

What is a heat wave under the California standard?

A specific two-part test, not a weather report. 8 CCR 3395 defines a heat wave as any day in which the predicted high temperature for the day will be at least 80 degrees Fahrenheit and at least ten degrees Fahrenheit higher than the average high daily temperature in the preceding five days. Both conditions have to be met. That means a 96 degree day in a week of 94 degree days is not a heat wave, and an 84 degree day after a run of 70s is. During a heat wave all employees must be closely observed by a supervisor or designee.

What is acclimatization and how should employers address it?

8 CCR 3395 defines acclimatization as temporary adaptation of the body to work in the heat that occurs gradually on exposure, and states that it peaks in most people within four to fourteen days of regular work for at least two hours per day in the heat. Two duties follow. An employee newly assigned to a high heat area must be closely observed by a supervisor or designee for the first 14 days of employment. And during a heat wave, all employees must be closely observed. The practical consequence is that the new hire and the worker back from vacation are the two highest risk people on the crew, and both are usually treated as routine.

What emergency response procedures must an employer implement?

Under 8 CCR 3395 the employer must ensure effective communication so an employee can contact a supervisor or emergency medical services, respond to signs and symptoms of heat illness with first aid or emergency medical services, and take immediate action on the serious indicators the standard names: decreased level of consciousness, staggering, vomiting, disorientation, irrational behavior or convulsions. The line that decides most citations is this one: an employee showing signs of heat illness shall not be left alone or sent home without being offered onsite first aid or being provided emergency medical services. Sending someone home to sleep it off is the violation.

What are the required training elements for the outdoor standard?

8 CCR 3395 requires employee training before work begins, covering environmental and personal risk factors, the employer's own procedures for water, shade, cool-down rests and first aid, the importance of frequent water consumption of up to four cups per hour, the concept and methods of acclimatization, the types of heat illness with their signs and symptoms, the importance of reporting symptoms in themselves and in coworkers, the employer's emergency response procedures, and how to give clear directions to the worksite. Supervisors get all of that plus their own implementation procedures, what to do when symptoms are reported or observed, and how to monitor weather and respond to hot weather advisories.

What written procedures must an employer develop for outdoor heat?

A written Heat Illness Prevention Plan, in English and in the language understood by the majority of the employees, available at the worksite, under 8 CCR 3395. It must contain procedures for providing water, procedures for access to shade, the high-heat procedures where they apply, emergency response procedures, and acclimatization methods and procedures. The plan may be integrated into the Injury and Illness Prevention Program required by 8 CCR 3203 rather than kept as a separate document.

Where does the California indoor heat standard apply?

8 CCR 3396 applies to all indoor work areas where the temperature equals or exceeds 82 degrees Fahrenheit when employees are present. It took effect on 23 July 2024, which makes it recent enough that a plan written before that date does not address it at all. If your heat plan predates July 2024 it is an outdoor plan, whatever it is titled.

What is meant by indoor places of employment?

8 CCR 3396 defines indoor as a space under a ceiling or overhead covering that restricts airflow and enclosed along its entire perimeter by walls, doors, windows, dividers, or other physical barriers that restrict airflow, whether open or closed. Read that carefully, because the phrase whether open or closed does a lot of work. A warehouse with every roll-up door open is still indoors. So is a shop, a mechanical room, an unconditioned equipment closet, a garage, and an attic. Employers who assumed the rule was about factories are usually surprised by how much of their operation it covers.

What are the exceptions to the indoor heat standard?

8 CCR 3396 lists four. Teleworking from a location the employee chooses and the employer does not control. Incidental heat exposures, defined below. Emergency operations directly involved in protecting life or property. And certain correctional facilities, including prisons, local detention facilities and juvenile facilities operated by government. There is also a narrower carve-out: where the work area does not meet the subsection (e) conditions, the control measure requirements do not attach, but water, cool-down areas, training, emergency response and the written plan still do.

What is the incidental heat exposure exception?

A narrow one. 8 CCR 3396 does not apply to incidental heat exposures where an employee is exposed to temperatures at or above 82 degrees Fahrenheit and below 95 degrees Fahrenheit for less than 15 minutes in any 60-minute period. Both halves must hold. Above 95 degrees the exception is gone regardless of duration, and past 15 minutes in the hour it is gone regardless of temperature. The exception also does not rescue two situations the standard names specifically: vehicles without effective and functioning air conditioning, and shipping or intermodal containers during loading and unloading.

What triggers the indoor control measures?

Any one of four conditions, under subsection (e) of 8 CCR 3396. Temperature at or above 87 degrees Fahrenheit. Heat index at or above 87 degrees Fahrenheit. Employees wearing clothing that restricts heat removal and temperature at or above 82 degrees. Or employees working in a high radiant heat area and temperature at or above 82 degrees. Two thresholds, 82 and 87, and which one applies depends on the clothing and the radiant heat, not on the calendar.

What is a high radiant heat area?

8 CCR 3396 defines it as a work area where the globe temperature is at least five degrees Fahrenheit greater than the temperature measured by a dry bulb thermometer. That is a measurable test with a specific instrument, not a judgment call. It also means an employer who wants to know whether the 82 degree trigger applies has to own a globe thermometer, or hire someone who does.

What is an acceptable way to measure indoor temperature and heat index?

8 CCR 3396 requires measurement when subsection (e) reasonably appears applicable, taken at the times of greatest heat exposure, and repeated when readings are reasonably expected to be 10 degrees Fahrenheit or more above the previous measurement. The record must show the date, the time, the specific work location, and whichever value is greater, the temperature or the heat index. Measuring on a mild morning to establish a comfortable baseline does not satisfy this, because the standard specifies the times of greatest exposure.

What records must be kept and for how long?

Under 8 CCR 3396, records of temperature and heat index measurements must be retained for 12 months or until the next measurements are taken, whichever is later. Each record carries the date, time, specific work location and the greater of the temperature or the heat index. This is the requirement most employers discover during an inspection rather than before one, because there is no annual filing that prompts it.

What are engineering controls and when must they be used?

They come first in the hierarchy under 8 CCR 3396. Where subsection (e) applies, the employer must use engineering controls to reduce the temperature or heat index below the trigger, or to the lowest feasible level if getting below the trigger is not feasible. Engineering controls change the environment rather than the worker's behavior: ventilation, air conditioning, cooling fans, evaporative coolers, insulation on hot surfaces, and shielding from radiant heat sources.

What are administrative controls and when must they be used?

Second in the hierarchy, under 8 CCR 3396, and only where feasible engineering controls are not sufficient to bring the area below the trigger. Administrative controls change how and when the work is done: shifting work to cooler parts of the day, rotating employees, adjusting work and rest schedules, reducing work intensity, and adding more people to the task.

What is personal heat-protective equipment and when must it be used?

Last in the hierarchy under 8 CCR 3396, required only where feasible engineering controls are not sufficient and feasible administrative controls do not minimize the risk. It is equipment worn to reduce heat strain, such as cooling vests, water-cooled or air-cooled garments, and heat-reflective clothing. The ordering matters legally. An employer who hands out cooling vests and skips the engineering assessment has satisfied the last step of a hierarchy without satisfying the first two.

What is considered a cool-down area?

Under 8 CCR 3396 a cool-down area must be maintained at less than 82 degrees Fahrenheit unless the employer demonstrates that is infeasible, blocked from direct sunlight and shielded from other high radiant heat sources to the extent feasible, large enough to accommodate the employees on recovery or rest so they can sit in a normal posture without physical contact, and located as close as practicable to where the work is. It may be an indoor or an outdoor area.

What must an employer do when a worker takes a preventative cool-down rest?

Under 8 CCR 3396 employees must be allowed and encouraged to access a cool-down area whenever they feel the need, for a period of at least five minutes plus the time it takes to get there and back. The employer must monitor the employee for signs and symptoms of heat illness, ask whether they are experiencing any, and not order them back to work until the symptoms have gone. A worker showing symptoms triggers the emergency response procedures, not a return to the task.

What must the indoor written plan contain?

8 CCR 3396 requires the written Heat Illness Prevention Plan to be in English and in the language understood by the majority of the employees, kept at the worksite and available on request. It must cover procedures for providing water, procedures for access to cool-down areas, the procedures for measuring and recording temperature and heat index and for assessing and implementing control measures, emergency response procedures, and acclimatization methods and procedures. A California employer with both indoor and outdoor exposure needs both sets of procedures, not one plan that mentions heat.

Is there a federal OSHA heat standard?

No. There is no federal heat standard in effect. Federal OSHA enforces heat hazards under Section 5(a)(1) of the Occupational Safety and Health Act of 1970, the General Duty Clause, which requires an employer to provide a workplace free from recognized hazards. OSHA uses wet bulb globe temperature to determine whether a heat hazard was present when it makes an enforcement decision. A proposed rule, Heat Injury and Illness Prevention in Outdoor and Indoor Work Settings, was published on 30 August 2024. The comment period closed 14 January 2025, an informal public hearing ran from 16 June to 2 July 2025, and the post-hearing comment period closed 30 October 2025. As of today the rule is not final and OSHA has published no target date.

What is OSHA's heat National Emphasis Program?

A programmed inspection initiative for outdoor and indoor heat-related hazards, directive CPL 03-00-024, effective 10 April 2026. An NEP directs OSHA to run programmed inspections in targeted industries rather than waiting for a complaint or an incident. Because there is no federal heat standard, an inspection under this program that finds a hazard is cited under the General Duty Clause, which means the employer's own written program and training records become the evidence on both sides.

Which states have their own heat rules?

OSHA's own heat page names five states with specific laws governing occupational heat exposure: Washington, Minnesota, California, Oregon and Colorado. California is the deepest, with 8 CCR 3395 covering outdoor work and 8 CCR 3396 covering indoor work. Other states have adopted or are moving on heat rules and OSHA's list lags. We do not publish a state-by-state table here, because a stale compliance table is worse than none. Verify any state other than California against that state's own regulator before you rely on it.

Get your heat program checked before the inspection

M Squared Safety writes and audits Heat Illness Prevention Plans for indoor and outdoor exposure, trains employees and supervisors to both curricula, and runs the measurement and recordkeeping the indoor standard requires. Call 949-954-6581 or use the contact page. Consulting and training are delivered nationwide, with California work from San Clemente across our service area.