Wildfire Smoke - Cal/OSHA

When wildfire smoke settles over a California job, the crew can usually smell it and see the orange light. What they cannot see is the part that does the damage: PM2.5, particles small enough to get deep into the lungs. A hazy sky can hide a dangerous reading, and a clear-looking morning can turn by noon. This Cal/OSHA Wildfire Smoke Toolbox Talk covers Title 8, Section 5141.1, the California rule that replaces the crew's eyes with a number — the Air Quality Index for PM2.5 — and tells the employer what to do at each level.

Where the boundary of this talk sits#

This talk covers what Section 5141.1 requires when wildfire smoke reaches a worksite. How respirators work, how to fit and wear them, and the full respiratory protection program belong to the respiratory protection talk. Heat, which often comes with fire season, belongs to the heat talks.

The anchor#

Here is the distinction that carries this whole talk: the smoke you can see is not what the rule measures — Section 5141.1 is triggered by the current AQI for PM2.5, particles too small to see, checked at the start of the shift and throughout it — so "it doesn't look that bad" is not a reading; at 151 the rule applies and N95s must be available to everyone, and above 500 respirators become mandatory, whether the sky looks orange or not.

Who the rule covers#

Section 5141.1(a)(1) applies to workplaces where the current AQI for PM2.5 is 151 or greater and the employer should reasonably anticipate that employees may be exposed to wildfire smoke. Outdoor construction is the obvious case.

Section 5141.1(a)(2) exempts:

• enclosed buildings or structures where the air is filtered by a mechanical ventilation system, with windows, doors, and other openings kept closed except when necessary to go in or out;
• enclosed vehicles where the air is filtered by a cabin air filter, with windows and doors closed except when necessary to go in or out;
• workplaces where the employer demonstrates, by measuring PM2.5 under the method in the rule's Appendix A, that the concentration does not exceed the equivalent of an AQI of 151;
• employees exposed to a current AQI for PM2.5 of 151 or greater for a total of one hour or less during a shift;
• firefighters engaged in wildland firefighting.

Two notes for construction. An equipment operator in a closed cab with a working cabin filter may be exempt — but not the laborer standing next to the machine, and not the operator once the door is propped open. And the one-hour exemption counts total time during the shift, not a single stretch.

Step one: check the AQI, and keep checking#

Section 5141.1(c) requires the employer to determine employee exposure to PM2.5 at the start of each shift and periodically after that. Acceptable sources include the U.S. EPA's AirNow, the Interagency Wildland Fire Air Quality Response Program, the U.S. Forest Service, the California Air Resources Board, and the local air pollution control district — or the employer can measure PM2.5 at the worksite and convert it to an AQI using the method in Appendix A. Smoke moves with the wind. A reading at 6 a.m. says nothing about 2 p.m.

Step two: tell the crew, and let them tell you#

Section 5141.1(d) requires a system for communicating wildfire smoke hazards in a language and manner readily understandable by employees, including provisions that encourage employees to inform the employer of wildfire smoke hazards without fear of reprisal. The system must tell employees the current AQI for PM2.5 and the protective measures available to them. It must also encourage employees to report worsening air quality and adverse symptoms that may come from smoke exposure — the rule names asthma attacks, difficulty breathing, and chest pain. A worker who is struggling to breathe has to be able to say so without being seen as complaining.

Step three: controls, in order#

When the current AQI for PM2.5 is 151 or greater, Section 5141.1(f) sets the order of controls.

Engineering controls first. Wherever feasible, reduce exposure to PM2.5 to below an AQI of 151 — for example, by providing an enclosed structure with filtered air where work can happen.

Administrative controls next. Where engineering controls are not feasible or not enough, use administrative controls when practicable. The rule gives examples: relocating work to a location where the AQI is lower, changing work schedules, reducing work intensity, or providing additional rest periods. On a construction site that can mean moving the dustiest, hardest work to the day the smoke lifts, or shifting a crew to interior work in a filtered building.

Respirators last — but always available. Section 5141.1(f)(3)(A) requires that, when the current AQI for PM2.5 is 151 to 500, the employer provide a sufficient number of respirators to all employees for voluntary use. These must be NIOSH-approved devices that effectively protect against PM2.5, such as N95 filtering facepiece respirators. Because this use is voluntary, the rule's note says fit testing and medical evaluations under Section 5144 are not required for employees whose only respirator use is voluntary use of filtering facepieces such as N95s.

Above 500: respirators are required#

Section 5141.1(f)(3)(B) changes the rule when the current AQI for PM2.5 exceeds 500. Respirator use is then required, under the full respiratory protection standard in Section 5144, and the employer must provide respirators with an assigned protection factor that reduces the wearer's exposure to below the equivalent of an AQI of 151. At that level, voluntary N95s handed out at the gate are no longer enough: the program, the fit testing, and the medical evaluation that come with Section 5144 apply.

Step four: training#

Section 5141.1(e) requires employers to provide effective training and instruction to all employees covered by the rule, and it refers to the rule's Appendix B for the required information. A crew should know where the AQI comes from, what the numbers mean, what the employer will do at each level, and how to wear the N95s they are given.

Where the duty sits#

8 CCR 5141.1 carries the duty: (a) scope at AQI 151 and the exemptions; (c) checking the AQI at shift start and periodically; (d) communication and reporting without reprisal; (e) training per Appendix B; (f) engineering, administrative, and respiratory controls, with voluntary N95s at 151 to 500 and required respirators above 500. 8 CCR 5144 is the respiratory protection standard that applies above 500. 8 CCR 3203 is the Injury and Illness Prevention Program the communication duty builds on.

What can go wrong?#

• Nobody checks the AQI because "it doesn't look that bad."
• The morning reading is 120 and nobody checks again when the wind turns.
• N95s are "in the office somewhere" instead of handed out.
• An operator props his cab door open for air and loses the enclosed-vehicle exemption.
• A worker with asthma tightens up but says nothing because he doesn't want to look weak.
• At an AQI over 500, the crew keeps working with loose N95s and no fit testing.

How do we manage this properly?#

• Check the AQI for PM2.5 — at shift start and periodically, from an approved source.
• Tell the crew the number — and what protection is available.
• Invite reports — worsening air and symptoms like difficulty breathing or chest pain, without reprisal.
• Control in order — filtered enclosures, then relocation, schedule changes, lighter work, more rest.
• N95s for everyone at 151 — enough for all, for voluntary use.
• Above 500, full program — required respirators under Section 5144.

Before you start#

Pull today's AQI for PM2.5 and say it out loud. Name who will check it again and when. Show where the N95s are. Point out the filtered building or cab crews can move to, and remind everyone how to report symptoms.

Talk it over#

• What is the AQI for PM2.5 right now, and where did we get it?
• Where are the N95s, and do you know how to put one on so it seals?
• Who would you tell if you started having trouble breathing?

The bottom line#

In California, wildfire smoke is measured, not eyeballed. Check the AQI for PM2.5 at the start of each shift and throughout it. At 151 or more, tell the crew, use filtered enclosures and administrative controls where you can, and make N95s available to everyone. Above 500, respirators are required under the full respiratory protection program.

Frequently asked questions about Cal/OSHA wildfire smoke rules#

Do we have to fit test N95s for wildfire smoke?

Not when the current AQI for PM2.5 is 151 to 500 and the use is voluntary. Section 5141.1 says fit testing and medical evaluations under Section 5144 are not required for employees whose only respirator use is voluntary use of filtering facepieces such as N95s. When the AQI exceeds 500, respirator use becomes required and Section 5144 applies.

Does the rule apply to an operator in an enclosed cab?

Not if the vehicle is enclosed, the air is filtered by a cabin air filter, and the windows and doors stay closed except when necessary to enter or exit. The exemption ends when the doors or windows are left open.

Download the Cal/OSHA wildfire smoke toolbox talk PDF#

Download this Cal/OSHA Wildfire Smoke Toolbox Talk as a printable PDF in English and Spanish, and review it before fire season, not during it.

Related toolbox talks#

• Respiratory Protection
• Extreme Weather
• Heat Stress
• Dust and Silica

Sources#

• Cal/OSHA, Title 8 CCR §5141.1 — Protection from Wildfire Smoke ((a)(1) current AQI for PM2.5 of 151 or greater; (a)(2) exemptions for filtered enclosed buildings and vehicles, measured AQI not exceeding 151, one hour or less per shift, wildland firefighters; (c) check AQI at shift start and periodically; (d) communication and reporting without reprisal; (e) training per Appendix B; (f)(1)–(2) engineering and administrative controls; (f)(3)(A) respirators for voluntary use at AQI 151–500, fit testing and medical evaluation not required for voluntary N95 use; (f)(3)(B) required respirators under §5144 above AQI 500): https://www.dir.ca.gov/title8/5141_1.html

Written by FieldSafetyTalk's safety professional — a CSP, ASP, CHST and OSHA Authorized Outreach Trainer with 14+ years of international construction safety experience across federal, heavy civil, and industrial projects.

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