Frequently Asked Questions Related to Indoor Heat Illness Prevention

These FAQs include information on Heat Illness Prevention in Indoor Places of Employment. For questions related to outdoor work, see the FAQs for Outdoor Places of Employment.

1. Where does this standard apply?
2. What are the exceptions?
3. When must employers implement all of the requirements of the regulation, including assessing worker heat exposures and implementing heat control measures?
4. What is meant by “indoor places of employment”?
5. What is an acceptable way to measure the indoor temperature?
6. What is the heat index and how is it measured?
7. What are the environmental risk factors for heat illness?
8. What is considered sufficient access to drinking water?
9. What is the required amount of water and what are effective procedures for replenishment?
10. What is meant by encouraging workers to drink water?
11. What is considered a cool-down area?
12. What is considered sufficient access to cool-down areas?
13. What is meant by encouraging workers to rest in cool-down areas?
14. What must an employer do when a worker takes a preventative cool-down rest?
15. What emergency response procedures must an employer implement?
16. What is acclimatization, and how should employers address it under the indoor heat illness prevention standard?
17. How is training evaluated for compliance with the standard?
18. What are the required training elements?
19. What are engineering controls and when must they be used?
20. How can an employer demonstrate that engineering controls are infeasible?
21. What are administrative controls and when must they be used?
22. What is personal heat-protective equipment and when must it be used?
23. What written procedures does an employer need to develop to comply with the requirements of this standard?
24. Where can I get more information on heat illness?

1. Where does this standard apply?

   With exceptions, this standard applies to all indoor work areas where the temperature equals or exceeds 82 degrees Fahrenheit 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.

2. What are the exceptions?

   This standard does not apply to:

   • Prisons, local detention facilities, and juvenile facilities.
   • Places of employment where workers are teleworking that are not under the control of the employer.
   • Emergency operations that are directly involved in the protection of life or property.
   • Incidental heat exposures where a worker 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. This exception does not apply to:
   • Vehicles without effective and functioning air conditioning.
   • Shipping or intermodal containers during loading, unloading, or related work.
3. When must employers implement all of the requirements of the regulation, including assessing worker heat exposures and implementing heat control measures?

   When one or more of the following conditions exist:

   • The temperature equals or exceeds 87 degrees Fahrenheit when workers are present.
   • The heat index equals or exceeds 87 degrees Fahrenheit when workers are present.
   • Workers wear clothing that restricts heat removal and the temperature equals or exceeds 82 degrees Fahrenheit.
   • Workers work in a high radiant heat area and the temperature equals or exceeds 82 degrees Fahrenheit.
4. What is meant by “indoor places of employment”?

   Indoor places of employment are spaces that are under a ceiling or overhead covering that restricts airflow and enclosed along the entire perimeter by walls, doors, windows, dividers, or other physical barriers that restrict airflow, whether open or closed. Generally, any workplace with a roof and enclosed sides is considered an indoor workplace.

   Work areas that are not indoors are considered outdoors and covered by California Code of Regulations Title 8, section 3395, Heat Illness Prevention in Outdoor Places of Employment. Indoor place of employment does not refer to a shaded area that is used exclusively as a source of shade and cooling for workers working in hot outdoor environments. Partial structures such as lean-tos and structures with one or more open sides are outdoor workplaces.

5. What is an acceptable way to measure the indoor temperature?

   Temperature can be measured with a thermometer that is freely exposed to the air but shielded from radiant heat sources, such as the sun, hot objects, hot surfaces, hot liquids, and fire. This air temperature must be measured in the immediate area where workers are located and recorded in degrees Fahrenheit.

6. What is the heat index and how is it measured?

   The heat index is what the temperature feels like to the human body when the effect of relative humidity is combined with that of the air temperature. There are two ways to determine the heat index:

   • Use a heat index monitor that measures both temperature and relative humidity and utilizes National Weather Service heat index equations to determine the heat index.
   • Calculate the heat index by measuring the indoor temperature with a thermometer (as mentioned in Q&A number 5 above) and relative humidity with a hygrometer, then use the chart found in Appendix A of Title 8, section 3396.
7. What are the environmental risk factors for heat illness?

   Environmental risk factors for heat illness are defined by the standard as conditions that create the possibility that heat illness could occur. These include:

   • Air temperature
   • Air movement
   • Relative humidity
   • Radiant heat from the sun and other sources, like machinery, stoves, ovens, etc.
   • Conductive heat sources, like the floor
   • Workload severity and duration
   • Protective clothing and personal protective equipment worn by workers
8. What is considered sufficient access to drinking water?

   Adequate water is required at all times and must be made available at no cost to the worker. The water must be potable (i.e., fit to drink), fresh, pure, suitably cool, and provided to workers free of charge. To ensure that water is fresh, pure, and suitably cool, Cal/OSHA advises employers or supervisors to visually examine, smell/taste the water, and pour some on their skin.

   Water must be located as close as possible to the areas where workers are working and in indoor cool-down areas. To encourage workers to drink water often, potable drinking water must always be available in locations readily accessible to all workers. Otherwise, if it is inconvenient to drink water, workers will be less likely to drink enough water to prevent heat illness.

   This may require placing water strategically in multiple locations, such as when workers are working in large areas. For example, in a large warehouse, water should be placed in safely accessible locations throughout the building in all areas where workers are working.

9. What is the required amount of water and what are effective procedures for replenishment?

   When drinking water is not from a plumbed system or otherwise continuously supplied, the employer must provide enough water for every worker to be able to drink one quart of water, or four eight-ounce cups, per hour for the entire shift.

   If an employer does not provide the full-shift quantity of drinking water at the start of a work shift (e.g., two gallons per worker for an eight-hour shift), the standard requires effective written procedures for drinking-water replenishment. In this case, a sufficient quantity of water must always be available and readily accessible, allowing every worker to consume at least one quart of water per hour until the water supply is replenished. Employers may supply workers with individual water bottles or containers as long as hygiene is ensured (i.e., clean bottles for each worker) and the water is replenished.

   An employer is out of compliance if at any time drinking water is not available to workers or if the practice is to wait until the water container is empty to replenish it. It is similarly impermissible for an employer to replenish the drinking water only when requested by workers.

10. What is meant by encouraging workers to drink water?

    The standard requires not only that water be provided, but that employers remind and encourage workers to drink it frequently. Workers should be reminded throughout the work shift to drink plenty of water. Workers often feel that they are there to work, and many of them may not feel how urgently their bodies need water.

    In their worker training sessions, employers must emphasize the importance of drinking water frequently throughout the day, especially in high heat. In addition, the employer must specify in their written heat illness prevention plan how the workers will be reminded and encouraged to drink water. For example, the supervisor can verbally remind workers or use an audible signal to remind workers to drink water.

    By removing any barriers that may exist to access, making the access distance as short as practicable, and making the water station inviting, employers can encourage the frequent drinking of water.

11. What is considered a cool-down area?

    Cool-down area means an indoor or outdoor area that is blocked from direct sunlight and shielded from other high-radiant heat sources and is either open to the air or provided with ventilation or cooling. Blockage is sufficient when objects do not cast a shadow in the area of blocked sunlight.

    The temperature in indoor cool-down areas must be maintained at less than 82 degrees Fahrenheit unless the employer demonstrates it is infeasible.

    A cool-down area does not include a location where any of the following conditions exist:

    • Environmental risk factors do not allow the body to cool down.
    • Workers are exposed to unsafe or unhealthy condition.
    • Workers are deterred or discouraged from accessing or using the cool-down area.
12. What is considered sufficient access to cool-down areas?

    Employers should provide and maintain one or more cool-down areas at all times while workers are present. The cool-down area shall be located as close as possible to the areas where workers are working.

    Cool-down areas must be large enough so that workers can sit in a normal posture fully in the cool-down area without having to be in physical contact with each other. Cool-down areas must also be large enough to accommodate the number of workers on recovery or rest period and the number of workers who remain on site during the meal period.

13. What is meant by encouraging workers to rest in cool-down areas?

    The employer is required to allow and encourage workers to take a cool-down rest in a cool-down area for a period of no less than five minutes at a time when they feel the need to do so to protect themselves from overheating. Waiting until symptoms appear before taking a cool-down rest may be too late. It is crucial that workers not be rushed while taking the cool-down rest, since the purpose of the cool-down rest is to reduce heat stress on the worker.

    Encouraging workers to take a cool-down rest in cool-down areas is especially important for workers who are paid on a piece-rate basis, as they would be less inclined to use this preventive rest.

    Water must be available in the cool-down area so that workers are encouraged to drink more water.

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

    Workers must be monitored during a cool-down rest and asked if they are experiencing any symptoms of heat illness, including simple fatigue. If any signs or symptoms of heat illness are observed or reported, the employer must not order the worker back to work and must continuously observe the worker until the signs or symptoms have gotten better. Common early signs and symptoms of heat illness may include pale skin, heavy sweating, headache, muscle cramps, and fatigue. If no sign or symptom of heat illness is observed or reported, monitoring may be periodic rather than continuous.

    If heat illness is suspected, appropriate first aid and emergency response procedures (if necessary) should be initiated without delay. No worker with signs or symptoms of heat illness should be left unattended or sent home without being offered onsite first aid or provided emergency medical services.

15. What emergency response procedures must an employer implement?

    Emergency medical services must be provided as quickly as possible if a worker suffers from heat illness. Any worker must be allowed to call for emergency medical services when necessary. In addition, the employer must ensure effective communication by voice, observation, or electronic means is maintained so that workers at the worksite can contact a supervisor or emergency medical services when necessary.

    Employers must have specific procedures to ensure that supervisors and workers are trained to recognize the signs and symptoms of heat illness, provide basic first aid (such as cooling towels and shade), obtain emergency medical services, and not allow a worker with signs or symptoms of heat illness to be left alone or sent home without being offered onsite first aid or provided with emergency medical services. Employers must be prepared to transport workers safely to a place where they can be reached by an emergency medical provider when necessary. The goal is to stop the rapid progression to more serious illness, which can include mental confusion, loss of consciousness, seizures, and death.

16. What is acclimatization, and how should employers address it under the indoor heat illness prevention standard?

    Acclimatization is a process by which the body adjusts to increased heat exposure. The body needs time to adapt when working in hotter environments. Workers are more likely to develop heat illness if they are not used to a job that newly exposes them to heat. Acclimatization is fully achieved in most people within 4 to 14 days of regular work involving at least 2 hours per day in the heat.

    A supervisor or designated worker must closely observe workers who have been newly assigned to any of the following, for the first 14 days of assignment:

    • A work area where the temperature or heat index, whichever is greater, reaches at least 87 degrees Fahrenheit.
    • A work area where the temperature or heat index, whichever is greater, reaches at least 82 degrees Fahrenheit where workers wear clothing that restricts heat removal.
    • A high-radiant-heat area where the temperature reaches at least 82 degrees Fahrenheit.

    In addition, all workers must be closely observed during a heat wave where no effective engineering controls are in use to control the effect of outdoor heat on indoor temperature. Best practices include finding ways to lessen the intensity of workers' work during a heat wave and during the 14-day break-in periods of new workers and those workers who have been newly assigned to a high-heat area.

    For purposes of this standard, "heat wave" means any day in which the predicted high temperature for the day will be at least 80 degrees Fahrenheit and at least 10 degrees Fahrenheit higher than the average high daily temperature for the preceding 5 days.

17. How is training evaluated for compliance with the standard?

    Cal/OSHA evaluates training compliance by examining both content and how it is presented. To be effective, training must be given in a language and at an educational level the workers understand. The test of compliance is whether training has occurred, whether the required content has been provided (see Q&A number 18 below), and whether the training has been effective in communicating the information to workers.

    Training must be provided before beginning any work involving a risk of heat illness. Training must be accurately documented.

18. What are the required training elements?

    An employer needs to provide training to both workers and supervisors on several topics, including the steps the employer is taking to comply with this regulation. Required topics include:

    • Environmental and personal risk factors for heat illness.
    • The employer’s procedures for complying with this regulation.
    • The importance of frequent water consumption.
    • The importance and methods of acclimatization.
    • Signs and symptoms of the different types of heat illness.
    • The importance of workers immediately reporting to the employer signs and symptoms of heat illness in themselves or co-workers.
    • The employer’s procedures for responding to signs and symptoms of heat illness, such as first aid.
    • Emergency response procedures, including contacting emergency medical services with clear directions to the worksite.
    • Prior to supervising workers, the supervisor must be trained in all of the information listed above and how to monitor and respond to hot weather reports, if the work area is affected by outdoor temperatures.
19. What are engineering controls and when must they be used?

    Engineering controls are methods of control or devices that remove or reduce heat or create a barrier between the worker and the heat. Employers have options when implementing control measures to protect their workers against heat illness and to comply with the standard. Examples include:

    • Increased natural ventilation, such as open windows and doors when the outdoor temperature or heat index is lower than the indoor temperature and heat index.
    • Cooling fans or air conditioning.
    • Local exhaust ventilation at points of high heat production or moisture (such as exhaust hoods in laundry rooms).
    • Reflective shields to block or reduce radiant heat.
    • Insulating or isolating heat sources from workers, or isolating workers from heat source.
    • Elimination of steam leaks.
    • Cooled seats or benches.
    • Evaporative coolers.

    Employers are required to use engineering controls when one or more of the following conditions exist:

    • The temperature equals or exceeds 87 degrees Fahrenheit when workers are present.
    • The heat index equals or exceeds 87 degrees Fahrenheit when workers are present.
    • Workers wear clothing that restricts heat removal and the temperature equals or exceeds 82 degrees Fahrenheit.
    • Workers work in a high-radiant heat area and the temperature equals or exceeds 82 degrees Fahrenheit.

    Employers must start with feasible engineering controls, then add administrative controls if those are not enough to reduce the temperature and heat index to below 87 degrees Fahrenheit (or temperature to below 82 degrees Fahrenheit for workers working in clothing that restrict heat removal or high-radiant heat areas).

20. How can an employer demonstrate that engineering controls are infeasible?

    Whether engineering controls are feasible to implement is a fact-sensitive question that includes an evaluation of the size, configuration and location of the indoor workspace, the sources of radiant heat, and the nature of the work being done by workers, among other things. Engineering controls may be infeasible because of technical reasons or due to excessively high cost of implementation. If an employer determines that implementation of engineering controls is infeasible, that would be evaluated on a case-by-case basis in the event of a compliance inspection.

21. What are administrative controls and when must they be used?

    “Administrative controls” refers to methods that limit exposure to heat by adjusting work procedures, practices, or schedules. Administrative controls should be used once all feasible engineering controls have been implemented but are not enough to:

    • Reduce and maintain the temperature and heat index to below 87 degrees Fahrenheit when employees are present or
    • The temperature to below 82 degrees Fahrenheit where employees wear clothing that restricts heat removal or work in high radiant heat areas.

    Examples include:

    • Modify work schedules and activities to times of the day when the temperature is cooler or schedule shorter shifts, especially during heat waves. For newly hired workers and unacclimatized existing workers, gradually increase shift length over the first one to two weeks.
    • Require mandatory rest breaks in a cooler environment, such as a shady location or an air-conditioned building. The duration of the rest breaks should increase as heat stress rises.
    • Schedule work at cooler periods or times of day, such as early morning or late afternoon.
    • Rotate job functions among workers to help minimize exertion and heat exposure.
    • Reduce work intensity or speed.
    • Modify work clothing.
    • Mark heat sources clearly so if workers must work nearby, they are aware of the hazards.
    • Require workers to work in pairs or groups during extreme heat so they can monitor each other for signs of heat illness.
22. What is personal heat-protective equipment and when must it be used?

    Personal heat-protective equipment are special cooling devices that the worker wears to cool them off and can protect them in hot environments. If feasible engineering controls do not decrease the temperature enough and administrative controls do not minimize the risk of heat illness, then personal heat-protective equipment can be used to protect workers from heat exposure. Examples include:

    • Water and/or air-cooled garments, cooling vests, jackets, and neck wraps. The cooling source can be reusable ice packs or cooled air connected to an external source.
    • Supplied-air personal cooling systems.
    • Insulated suits.
    • Heat-reflective clothing.
23. What written procedures does an employer need to develop to comply with the requirements of this standard?

    The employer must develop, put in writing, and implement effective procedures for complying with the requirements of this standard. A compliant heat illness prevention plan (HIPP) includes the following subsections of title 8, section 3396:

    • Procedures for providing sufficient water, as described in subsection (c).
    • Procedures for providing access to cool down areas, as described in subsection (d).
    • Procedures to measure the temperature and heat index and record whichever is greater, identify and evaluate environmental risk factors for heat illness, and implement control measures, as described in subsection (e).
    • Emergency response procedures, as described in subsection (f).
    • Acclimatization methods and procedures, as described in subsection (g).

    A heat illness prevention plan that is little more than a restatement of the safety orders does not satisfy the standard; instead, it must be specific an customized to the employer’s operations. Workers and supervisors must be trained in these procedures so they understand and can implement the employer's plan.

    The HIPP must be written in both English and the language understood by the majority of workers. It must be available to workers at the work site, as well as to representatives of Cal/OSHA upon request. The plan will be considered available at the work site if, for example, it is accessible on a cell phone or other electronic device that is available for workers to use for this purpose upon request.

    The HIPP may be integrated into the employer's Injury and Illness Prevention Program required under T8 CCR 3203.

    Cal/OSHA offers a Written Model Program that can be used to help develop an HIPP.

24. Where can I get more information on heat illness?

    Numerous resources and heat illness publications can be found on Cal/OSHA’s Heat Illness Prevention webpage.

Revisions and Updates

• June 21, 2024
• Page created