Cal/OSHA Wildfire Smoke Rule: AQI 151 and Employer Duties

When the Air Quality Index for fine particulate matter reaches 151 and an employer should expect workers to be exposed to wildfire smoke, Cal/OSHA’s section 5141.1 applies. The employer must check the AQI at the start of each shift, communicate with workers, train them, reduce exposure where feasible, and provide N95 respirators for voluntary use. Above an AQI of 500, respirators are mandatory. Filtered buildings and vehicles, brief exposures, and wildland firefighters are exempt. Citations usually come from missing monitoring and training records.

When does the wildfire smoke rule apply?

When two conditions are met. Under section 5141.1(a)(1), the rule applies to workplaces where “The current Air Quality Index (current AQI) for PM2.5 is 151 or greater, regardless of the AQI for other pollutants,” and where “The employer should reasonably anticipate that employees may be exposed to wildfire smoke.”

An AQI of 151 is the start of the “Unhealthy” category. During a major fire, large parts of the state can stay above that level for days, and the rule can apply to workplaces far from the fire itself.

Which workplaces are exempt?

Five categories, listed in subsection (a)(2):

Enclosed buildings or structures with mechanically filtered air, where the employer keeps windows, doors, bays, and other openings closed except to enter or exit.

Enclosed vehicles with a cabin air filter, under the same closed-openings condition.

Worksites where the employer measures PM2.5 under Appendix A and shows the level doesn’t reach an AQI of 151.

Employees exposed for “a total of one hour or less during a shift.”

Firefighters engaged in wildland firefighting.

The exemptions depend on facts the employer must be able to prove. A warehouse with filtered air but loading bays left open for hours may not qualify. A delivery driver who spends most of the shift outside the truck may not either. The one-hour exemption needs time records or another way to show the total exposure.

What does the rule require when it applies?

Monitoring, communication, training, and controls.

Monitoring. Under subsection (c), the employer “shall determine employee exposure to PM2.5 for worksites covered by this section at the start of each shift and periodically thereafter,” using official sources such as AirNow, the California Air Resources Board, or the local air district, or by measuring at the worksite.

Communication and training. The employer must have a system for telling workers the current AQI and the protective measures available, and for encouraging workers to report worsening air or symptoms “without fear of reprisal.” Training must be in a language and manner workers understand and must include, at a minimum, the information in Appendix B to the regulation.

Controls. Subsection (f)(1) says the employer “shall reduce employee exposure to PM2.5 to less than a current AQI of 151 by engineering controls whenever feasible,” such as filtered buildings or vehicles. If that isn’t feasible or isn’t enough, the employer must use administrative controls if practicable, like relocating work, changing schedules, reducing intensity, or adding rest.

Respirators. Between an AQI of 151 and 500, the employer must provide enough NIOSH-approved respirators, such as N95s, for voluntary use, and encourage workers to use them. Fit testing and medical evaluations aren’t required for voluntary use of filtering facepieces. Above 500, subsection (f)(3)(B) states that “respirator use is required,” and the full respiratory protection program under section 5144 applies.

How should employers plan before smoke season?

With a written procedure that’s ready before the first bad-air day. The rule’s duties start the moment the AQI crosses 151, and there’s no grace period for an employer that hasn’t yet bought respirators or trained its crews. A workable plan names who checks the AQI for each worksite and when, what source they use, how the reading is recorded, and who decides on controls.

It also sets the controls in advance. For a construction or landscaping crew, that might mean moving work into filtered buildings or vehicles, shifting the schedule to hours with better air, or reducing physical intensity. For delivery and field service, it might mean keeping vehicle windows closed and limiting time outside. Writing down why a given control isn’t feasible matters too, because the rule requires engineering controls “whenever feasible,” and an inspector will ask.

Respirator stock is the practical bottleneck. During large fires, N95 supply can run short. Employers with outdoor workforces should keep enough on hand for several days of full-crew use and record when and to whom they’re distributed.

Where do wildfire smoke citations come from?

The same place most Cal/OSHA citations come from: documentation. An inspector will ask how the employer checked the AQI on the day in question, whether workers were trained before smoke season, what controls were considered, and whether respirators were actually handed out. An employer that did the right things but can’t show it is in a weak position.

Training is a common gap. The rule ties training to section 3203, the Injury and Illness Prevention Program, and it must contain the Appendix B information. Many employers wait until a fire starts to train, which leaves the first days of exposure undocumented. Building the training into the annual safety calendar avoids that problem.

The firm’s post on the outdoor heat illness rule covers a related standard that often applies on the same days, since fire season and heat season overlap.

What claims follow smoke exposure?

Citations first. But a worker who becomes ill can also file a workers’ compensation claim, and a known, uncorrected violation can support a serious and willful misconduct petition. Retaliation is the other exposure. The rule requires a system that lets workers raise smoke hazards without fear of reprisal, and Labor Code section 6310 prohibits retaliation against employees who complain about safety. A worker sent home or disciplined after objecting to working in heavy smoke has the start of a retaliation claim.

A worker who refuses to work in conditions they believe are unsafe raises harder questions. California law protects refusals in some circumstances involving a real and apparent hazard. Supervisors should be trained to escalate those situations, not respond with discipline.

When smoke season arrives or a complaint is filed

1. Preserve AQI checks, training records, respirator distribution logs, the communication system’s messages, and the supervisors’ emails and texts for the affected shifts, under a litigation hold.
2. Calendar any Cal/OSHA document requests and citation appeal deadlines, and notify the workers’ comp carrier and any EPLI policy.
3. Identify the supervisors and crews who worked during the smoke event, and make sure no one takes action against a worker who complained that could look like retaliation.
4. Pull the time records showing how long each crew worked outdoors, to support or rule out the one-hour exemption.
5. Talk to counsel before the Cal/OSHA interview, before settling a citation, and before responding to any related claim.

Safety disputes often run alongside employment claims. The firm’s page on California employment defense describes how those cases are handled.

Wildfire smoke rule questions

Does the rule apply to indoor workers?

Usually not, if the building’s air is filtered by a mechanical ventilation system and the employer keeps windows, doors, and bays closed except to enter or exit. Workplaces without filtered air, or where openings stay open, can be covered. Employers with partially open facilities, like warehouses with active loading docks, should assess whether the exemption fits.

Do employees have to wear the N95s?

Not when the AQI is between 151 and 500. In that range, the employer must provide respirators and encourage their use, but use is voluntary. Above 500, use is required, and the employer must follow the full respiratory protection program in section 5144, including fit testing and medical evaluations. Emergency operations follow a separate rule in the regulation.

How often does the employer have to check the AQI?

At the start of each shift and periodically after that, as needed to protect workers. Employers can use official websites like AirNow or the local air district, get readings by phone or text, or measure PM2.5 on site. An employer can skip the checks only if it assumes the AQI is above 500 and complies with the respirator requirements at that level.

Can an employer be cited if the fire is far away?

Yes. The rule applies based on the AQI where employees work and whether exposure is foreseeable, not on distance from the fire. Smoke can travel hundreds of miles. An employer in a city with an AQI over 151 from a distant fire has the same duties as one near the fire, unless an exemption applies.

If your company is facing a smoke-related citation or claim

If your company has received a Cal/OSHA citation, a complaint, or a claim tied to wildfire smoke exposure, the AQI records, the training, and the respirator logs usually decide how much of it is real. Rosenberger + Kawabata represents employers defending employment lawsuits and claims through its business litigation practice, including claims involving workplace safety and air quality. Contact Rosenberger + Kawabata online for a confidential consultation, or call (310) 894-6921.

Sources

The regulation is California Code of Regulations, title 8, section 5141.1. The statute is Labor Code section 6310.

This post is general information about California and federal employment law as of November 7, 2026. It is not legal advice, and reading it does not create an attorney-client relationship. Employment statutes, regulations, and court decisions change often, and the outcome of any claim depends on its facts. Past results do not guarantee future outcomes.