July 11, 2024Client Alert

Heat Safety Rule Proposed by Federal OSHA – California Rule Effective August 1, 2024

On July 2, 2024, OSHA released its proposed rule to strengthen private- and public-sector employers’ responsibilities to protect both indoor and outdoor employees from heat-related illness and death. OSHA must allow at least 120 days for comment before adopting a final rule. Generally, final rules are not completed in that short period of time. Depending on the outcome of the election, the Biden Administration may not have enough time to adopt a rule if the White House changes hands and the rule has not been finalized by early January. 

As summer continues, worker safety in both indoor and outdoor workplaces is important to keep in mind, since heat related illnesses can be fatal. Global temperatures are expected to continue to rise, therefore heat-related safety in the workplace presents a longer-term challenge. Employers should be proactive and implement measures to keep workers safe when extreme heat presents a safety hazard, and most employers are mindful of these hazards already. However, the OSHA final rule may establish specific regulations concerning written procedures about water, shade, breaks, acclimatizing workers, clothing, and monitoring workers. These rules may require employers to alter their current practices or face fines. 

The proposed rule is likely to change before implementation. There are likely to be legal challenges. Based upon the outcome of the election, there may be a halt of any rule that is adopted. Employers may decide to take a wait and see approach. However, OSHA is already targeting employers for heat inspections, through a heat enforcement directive that targets certain industries. So, it is important for employers to develop more formal plans to keep workers safe already, and not just rely on common sense practices.

Even without a rule, employers remain obligated to adhere to existing OSHA “general duty” requirements to protect workers. As climate challenges persist this summer (including power outages following extreme weather), OSHA will focus on worker heat illnesses and deaths to prove its case for a final rule. Industry efforts to protect workers will be watched closely, and some states (discussed below) have already passed regulations on the subject. A California rule (discussed below) is expected to become enforceable on August 1st.

Michael Best’s current recommendations, as well as what could eventually be required by the proposed rule, are summarized below.


In its current form, the proposed rule would require employers to develop and implement a written worksite heat injury and illness prevention plan (HIIPP). Most employers do not have a written plan, so this represents a change, and is something OSHA is already enforcing under its general duty clause which requires employers to “maintain a workplace free of recognized hazards that may cause death or serious bodily harm.” This written plan requirement would apply to those employers with more than 10 employees, while employers with 10 or less employees would not be required to put it in writing but would still be obligated to comply with the other requirements below.


Clothing can be a risk factor for heat-related injury or illness. Workers should wear lightweight, light colored, breathable clothing, if possible, to wear such clothing without compromising worker safety. Cotton is generally breathable and allows the body to cool down better than other fabrics. Reflective clothing that is designed to reflect radiant heat, such as vests, aprons, or jackets could be used. Cooling vests may be effective but can become an insulator when they reach the body’s temperature. Workers with outdoor jobs should wear hats to keep sun off their faces. Most employers require pants, and sometimes long sleeves for protection against cuts, rashes or burns, but these rules may need to be altered as the heat rises. One Michael Best client recently asked, “can we let some employees wear shorts and not others.” When it comes to safety, it is okay to provide different safety measures depending on the job. Allowing some employees relief from certain clothing requirements, where it is safe to do so, can allow a company to dedicate more attention and cooling resources to those who need to wear more protective clothing or gear.

The proposed rule requires employers whose employees must wear vapor-impermeable clothing (defined in the proposed rule as “full body clothing that significantly inhibits or completely prevents sweat produced by the body from evaporating into the outside air”), to evaluate heat stress hazards resulting from this clothing and implement policies and procedures to protect employees.


It is important to allow new workers that aren’t used to working in high heat environments, and returning workers that have been away from work, to acclimatize to the working environment. Current recommendations include using a staggered approach over 7-14 days to give these workers time to get used to working in hot environments. Employers should start workers with lower workloads and gradually increase the workload, so employees get used to working in the heat. This is especially important for summer youth or college workers who are just beginning to work as the heat rises. New employees are often less efficient and may overexert themselves, while trying to do a good job to “prove” themselves during their first few days. While this extra effort may be appreciated by employers, employers should ensure that new employees working in extreme heat conditions are kept safe. So education to offset this potential for overexertion may be necessary.

The proposed rule requires implementation of acclimatization protocols during an employee’s first week on the job, with different protocols for both new employees and returning employees. New employees would be required to gradually acclimatized, with the employee’s exposure to heat being restricted to no more than 20% of a normal work shift exposure on the first day of work, 40% on the second day, 60% on the third day, and 80% on the fourth day. For returning employees, gradual acclimatization to heat would be required in which employee exposure to heat is restricted to no more than 50% of the workload on the first day of work, 60% on the second day, and 80% of the third day.


A simple and effective way to keep workers safe is to ensure adequate opportunities for hydrationrest, and shade. Drinking water, other cool beverages (sports drinks, etc.), ice, and certain food items, such as popsicles, may be provided to workers. The current OSHA recommendation for water consumption is 1 cup of water every 20 minutes, not to exceed more than 48 oz. of water in an hour. Employers should ensure that there is enough water available, and that it is easily accessible. Workers should also be encouraged to hydrate properly before, during, and after work. Workers should not wait until they are thirsty to hydrate.

The proposed rule would require access to 1 quart of drinking water, per employee, per hour, when temperatures are at or above the initial heat trigger (“a heat index of 80° F or a wet bulb globe temperature equal to the National Institute for Occupational Safety and Health (NIOSH) Recommended Alert Limit”). The water must be placed in locations that are readily accessible, and suitably cool.


When heat is extreme, workers should be given more breaks, and encouraged to take breaks by supervisors. Workers should be encouraged to speak up if they are feeling too hot. Opportunities to rest in the shade is crucial for outdoor worksites. If there is not any naturally occurring shade, pop up tents can be used to create a shaded area. For indoor worksites, there should be a spot for workers to take breaks that is cooler, ideally air-conditioned, or with plenty of fans. Employers can also provide cool towels for workers to use to cool down. Some employers have rented water misting stations for workers to use in extreme heat.

The proposed rule would require frequent breaks based on the severity of the heat. Once ambient temperatures are at or above the high heat trigger (“a heat index of 90°F or a wet bulb globe temperature equal to the NIOSH Recommended Exposure Limit), workers must be given more breaks of at least 15 minutes every two hours. At outdoor work sites, artificial shade, or access to an enclosed space with air-conditioning is required. For indoor worksites, there must be an area for employees to take breaks that is in air-conditioned areas, or has increased air movement, such as using fans. The proposed rule emphasizes breaks and their importance to worker safety when temperatures are extreme. But it raises questions about pay for such breaks.


Employers should educate employees on personal risk factors that might make them more susceptible to heat illness, such as health conditions, medications, physical characteristics, and behavioral characteristics. Employers should train employees on recognizing signs of heat illness and heat emergencies. Urine output is one the best measures of hydration. Placing signs in restrooms that describe the level of hydration based upon urine color are effective education tools. 

The proposed rule would require employees to receive initial training before they begin work at or above the initial heat trigger. Each employee will be required to receive training and understand the following: heat stress hazards, heat-related injuries and illnesses and their risk factors, including the contributions of physical exertion, clothing, personal protective equipment, a lack of acclimatization, and personal risk factors, signs and symptoms of heat-related illness and which ones require immediate emergency action, the importance of removing PPE (such as gloves, boots, aprons, etc.) during rest breaks, importance of taking rest breaks to prevent heat-related illness or injury, and that rest breaks are paid, importance of drinking water to prevent heat-related illness or injury, the location of break areas, and the location of employer-provided water.


Employers should have a plan for a heat related incident. Headaches or nausea, weakness or dizziness, heavy sweating and dry, hot skin, elevated body temperatures, thirst, and decreased urine output can all be signs of heat illness. If a worker is exhibiting any of those signs, they should be assisted in cooling down. The worker can drink cool water, remove any unnecessary clothing, take a break in a cooler area, and cool down with ice, or a fan. These workers should be monitored in case medical care is necessary.

Heat emergencies are incredibly dangerous and can be fatal. Signs of a heat emergency include abnormal thinking or behavior, slurred speech, seizures, and loss of consciousness. If a worker is exhibiting those signs, 911 should be called immediately, and the worker should be cooled down right away, with water or ice (ice bath, etc.). Somebody should stay with the worker until help arrives. All of the above, should be built into a written heat emergency protocol to demonstrate the company commitment, and as a reference when heat emergencies arise. (See link under Cal/OSHA rule below for model plan.)

The proposed rule would require employers with more than 10 employees to develop and implement a written worksite Heat Injury and Illness Prevention Plan (HIIPP). Employers with 10 or fewer employees will still need a plan, but it can be communicated verbally. The HIIPP must be made available to each employee performing work at the site and in a language that each employee, supervisor, and heat safety coordinator understands. OSHA will require employers to evaluate the effectiveness of the plan annually, or whenever a heat-related illness or injury occurs that results in death, days away from work, medical treatment beyond first aid, or loss of consciousness. In developing and updating the HIIPP, employers will be required to seek input from nonmanagerial employees and their representatives.

If it is expected that the high heat trigger will be met, employers must notify their employees of the importance of drinking plenty of water, the employees’ right to take rest breaks if needed and the rest breaks required by the proposed rule, how to seek help and the procedures to take in a heat emergency, and the location of break areas and drinking water.

Finally, employers must develop a heat emergency response plan and ensure that supervisors and workers are trained to respond effectively to heat-related emergencies, including providing first aid and contacting emergency services.


The proposed rule requires employer plans to include monitoring procedures to observe employees for signs and symptoms of heat related illnesses. Employers must include one of the following procedures: a mandatory buddy system in which co-workers observe each other, or observation by a supervisor or heat safety coordinator (with no more than 20 employees observed per supervisor). For employees who are alone at a work site, employers must maintain a means of effective, two-way communication with those employees and make contact with the employees at least every two hours.


The proposed rule defines initial heat trigger and high heat trigger temperatures, and outlines requirements for both situations. When temperatures are at or above the initial heat trigger, employers must provide break areas with either artificial or natural shade, provide drinking water, and provide a plan for workers to adjust to the heat over several days by gradually increasing their workload. When temperatures are at or above the high heat trigger, employers must provide 15-minute paid rest breaks every two hours, monitor workers for signs of heat illness, issue a hazard alert warning for workers to stay hydrated, and check on employees working alone.

Once the final rule is published in the Federal Register, employers must comply with all requirements of the final rule within 150 days. Employers who fail to comply once the final rule is published could be at risk for fines.


While the OSHA proposed rule is months away from being implemented, the Cal/OSHA Standards Board implemented an indoor heat illness prevention rule, which becomes effective on August 1, 2024, that impacts California employers. This new rule applies when workers are present, and the indoor temperature equals or exceeds 82° F. When workers are present and the indoor temperature equals or exceeds 87° F, employers must take additional steps to keep workers safe, implementing all requirements of the regulation. Employers must attempt to reduce the indoor temperature to below 87° F with engineering controls, such as cooling fans or air-conditioning. Like the proposed OSHA rule, employers must provide at least one quart of suitably cool drinking water, per hour, to all workers in covered workplaces for the duration of their entire shift.

Employers must have at least one cool down area available for indoor workers to use during their shifts. A cool down area must be blocked from direct sunlight, shielded from high-radiant heat sources, and either be open to the air or have ventilation or cooling. These areas must be sufficient to accommodate all employees on recovery, rest, or meal periods. Additionally, employers will have to acclimatize new workers.

The new Cal/OSHA indoor heat rule requires employers to have a written heat illness prevention plan that includes procedures for providing sufficient water, providing access to cool down areas, measuring the temperature and heat index and recording whichever is greater, identifying and evaluating environmental risk factors for heat illness, implementing control measures, emergency response protocols, and acclimatization schedules.

Cal/OSHA has published a model written plan that employers can use as a starting point. That plan may also satisfy federal OSHA expectations for indoor employment.



Thank you to our summer associate, Hector Manzanarez, for his contributions to this alert.

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