How California OSHA’s Proposed Indoor Heat Illness Prevention Regulations May Affect Employers

Learn about California’s proposed indoor heat illness prevention standard, how it could affect employers, and how the standard is similar to the proposed Federal OSHA standard.

California experienced the worst heat wave in its history during the summer of 2022. According to, on September 7, 2022, 61 million people were under heat advisory warnings, with the majority of these people residing in California and Arizona. 

construction building crane hot sun

In preparation for extreme heat certain to hit different parts of the country in the summer of 2023, workplace safety regulators at both the federal and local levels continue to rethink heat illness prevention measures and develop regulations. California Occupational Safety and Health Administration (OSHA) is one of the agencies that has proposed regulations for indoor settings. Some of the key elements of these new regulations include:

  • Relying more on heat index measurements and limits rather than plain temperature measurements
  • Including both indoor and outdoor regulations and control requirements
  • Accounting for both weather-related heat and process-generated radiant heat sources
  • Adding allowances for what California OSHA terms “clothing that restricts heat removal”

This article further examines California’s proposed standard, how it could affect employers, and how the standard is similar to the proposed Federal OSHA standard being promulgated.

What Are California's Heat Illness Standards?

California OSHA is promulgating a separate indoor heat illness standard that has been in the works for several years. California, Washington, Minnesota, and Oregon all have their own heat illness prevention regulations in place now, but the new California standard is meant to join the California OSHA outdoor work heat illness prevention regulations currently in force.

The state's outdoor heat illness regulations have been in emergency and then permanent form since 2005. Additional research into heat illness incidents associated with indoor work between 2010 and 2018 caused a resurgence in interest in developing this new standard.

While the new standard is not final, it may still be helpful to read the regulation wording to become familiar with what could be incorporated into a final standard in the near future. There are some differences between the new indoor proposed standard and the existing outdoor standard (Title 8, 3395, Heat Illness Prevention in Outdoor Places of Employment), and employers may require a bit of adjustment when trying to comply with the new standard.

For example, the current outdoor standard focuses on degrees Fahrenheit only, while the new proposed indoor standard references both temperature in degrees Fahrenheit and heat index. index takes into account humidity and is found using the temperature in degrees Fahrenheit along with the percentage of relative humidity and plotting the heat index on the National Weather Service heat index chart.

OSHA Heat Index

Anywhere the new standard references a temperature such as 82 degrees Fahrenheit (F), it also mentions heat index. If an indoor space tends to have temperatures or a heat index over 87 degrees F, or 82 degrees F with employees wearing what Cal OSHA calls “clothing that restricts heat removal,” and that same workplace experiences moderate to high levels of humidity, this standard may be more challenging to comply with than it first seems.

The use of heat index numbers in the new standard could indicate a desire by California OSHA to include the same measurement requirement in the outdoor standard at some point in the future.

"Clothing that restricts heat removal” means full-body clothing covering the arms, legs, and torso that is any of the following:
(A) Waterproof; or
(B) Designed to protect the wearer from a chemical, biological, physical, radiological, or
fire hazard; or
(C) Designed to protect the wearer or the work process from contamination.There is an exception: “Clothing that restricts heat removal” does not include clothing with flame or arc-flash resistant properties demonstrated by the employer to be all of the following:

  1. Constructed only of knit or woven fibers; and
  2. Worn in lieu of the employee’s street clothing; and
  3. Worn without a full-body thermal or moisture barrier.

Expanded Heat Illness Assessment Procedures

Once a workplace reaches temperatures or a heat index of 87 degrees F, or 82 degrees F and employees are wearing “clothing that restricts heat removal,” the standard requires additional assessment and control measures to be completed.

Employers must measure heat index, but it doesn’t stop there. Somewhat parallel to the outdoor regulation standard requirements for “high heat procedures," the measures include assessment procedures such as:

  • Measuring both temperature and heat index
  • Identifying and evaluating all other environmental risk factors for heat illness
  • Keeping records of all measurements taken
  • Taking measurements during the time of greatest exposure
  • Taking measurements when it is suspected that measurements may be 10 degrees or more above the latest set of measurements
  • Retaining measurement records for 12 months or until the next set of measurements is taken, whichever is later
  • Using instruments that utilize the NWS heat index tables to measure heat index

OSHA Heat Removal Clothing

At the end of the assessment section, employers are given an option of having active employee and employee representative involvement in the assessment and planning or assuming that a work area falls under these control requirements and applying Section (e)(2) controls regardless.

Controls and Response: Comparing the Indoor and Outdoor Standards

Section (e)(2) outlines engineering controls, administrative controls, and personal heat protective equipment in ranked order of preference. For example, if an employer wishes to bypass engineering controls in favor of administrative controls or personal heat-protective equipment, they must be able to establish the infeasibility of the higher-ranked engineering control.

The emergency response section of the proposed standard is almost identical to the outdoor heat illness standard and requires effective communication with employees, supervisors, and emergency medical services. These plans will help to ensure an employee can be accessed by emergency medical providers, and that accurate directions to the workplace are given to emergency providers. The emergency response section also requires planning for and appropriate response to signs and symptoms of heat illness, including providing first aid and medical services and ensuring the affected employee is monitored and not left alone without being offered medical treatment.

Section (h) of the indoor heat illness regulation includes training topics for both employees and supervisors. These topics are identical to the training requirements found in the outdoor standard. However, allowances are made for the fact that shade is not a factor indoors and that weather monitoring may not play as large a role in some indoor workplaces.

Water provision, including a specific volume per employee per hour and a requirement for the water to be suitably cool, is included in both standards.

While shade is not a prominent topic in the indoor regulation, free access to a cool-down area is. Like in the outdoor regulation, employees must be allowed to access the area at all times, be monitored when in the area, encouraged to stay in the area, and not ordered back to work for at least five minutes and then only if all heat illness symptoms have abated.

The new indoor standard addresses acclimatization during heat waves by requiring close observation of employees if effective engineering controls for indoor temperatures are not in place. It also requires 14 days of close observation of newly assigned employees in workplaces where the indoor temperature or heat index equals or exceeds 87 degrees F or 82 degrees F in workplaces where employees must wear "clothing that restricts heat removal" or who work in high-radiant-heat areas.

Employers Would Need a Written Program

The written portion of this program can be included as part of the IIPP (Injury and Illness Prevention Program) or as part of a separate heat illness prevention plan. The written plan minimums include the following procedures:

  • Provision of water as outlined in the regulation
  • Access to cool-down areas as outlined in the regulation
  • Measurement of temperature and heat index as well as risk factor evaluation and control measures as outlined in the regulation
  • Emergency response
  • Close monitoring during acclimatization

For employers with warm indoor spaces, particularly for those with high humidity, radiant heat sources, and requirements for protective clothing, this standard could present compliance challenges including the requirement to have a written indoor heat illness prevention program, when the regulation is finalized. Until then, duty officers will continue to enforce indoor heat illness prevention under the general duty clause.

Federal OSHA Proposes Similar Regulations

The new California heat illness regulations mirrors some of the elements found in a proposed federal standard. The inclusion of indoor heat illness prevention provisions and the use of heat index measurements instead of straight temperature measurements are two of those reflective provisions. The text of the proposed federal regulation can be reviewed on

The proposed federal regulation appears to be in development to allow for easier and more specific enforcement of heat illness prevention measures. Currently, Federal OSHA is forced to rely on the general duty clause when issuing citations.

Since 2011, Federal OSHA has had a national emphasis program in place around heat illness prevention. That national emphasis program has resulted in more enforcement action including citations and site visits focused on heat illness prevention programming and the program is likely to continue into at least 2025. Employers with locations in Federal OSHA states may wish to review this article written about that program and the OSHA summary of the national emphasis program to learn more about industries being targeted, enforcement instructions for duty officers, and when employers might expect enforcement visits to occur.

If you have questions about these new proposals or other OSHA standards, contact your Woodruff Sawyer account team.



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