Compliance · Cal/OSHA
Cal/OSHA Protection from Wildfire Smoke (8 CCR §5141.1)
Occupational: outdoor work in wildfire smoke (California)
California's Protection from Wildfire Smoke regulation, 8 CCR §5141.1, in effect since 2021, is the clearest worker trigger for smoke in the United States. It applies when the current Air Quality Index for PM2.5 is 151 or greater and workers may reasonably be exposed; the regulation's own conversion table puts AQI 151 at 55.5 µg/m³ of PM2.5. From that level, employers must communicate the hazard, train workers, apply feasible engineering and administrative controls, and provide NIOSH-approved respirators such as N95s for voluntary use. Where the current AQI for PM2.5 exceeds 500 (above 500.4 µg/m³ in the regulation's table), respirator use is required.
The standard
What Cal/OSHA's Wildfire Smoke Rule Is
The "current AQI" means EPA's NowCast. The regulation's Appendix A table keeps the older AQI breakpoints. EPA's 2024 AQI revision places AQI 500 at 325.4 µg/m³, while AQI 151 is 55.5 µg/m³ under both.
Limit values
Cal/OSHA 5141.1 Limit Values
Every value Cal/OSHA publishes for the parameter below, with its averaging period, as the standard states it.
Who it applies to
Who Must Comply
Employers in California whose workers may be exposed to wildfire smoke outdoors, with exemptions for enclosed buildings and vehicles with filtered air, and for exposures of one hour or less during a shift at a current AQI of 151 or greater.
Monitoring
How Monitoring Demonstrates Compliance
Employers may check the current AQI from EPA AirNow and other agencies, or measure PM2.5 at the worksite with a direct-reading monitor that meets the regulation's Appendix A. The monitor must not underestimate exposure (or its error must be accounted for), must measure particles from 0.3 µm or less up to 2.5 µm, and must be calibrated and maintained as its manufacturer instructs, with results converted to the AQI. A worksite monitor shows the air the crew actually breathes, which can differ from the nearest regional station during a smoke event.
Recommended
best match-
Industrial monitor for indoor and outdoor sites. Built-in sensors cover the essentials, and hot-swappable gas sensor cartridges and a differential-pressure option add more.
Built-inPM2.5Gas 1
Free: one more gas sensor cartridge
Gas 2
Free: one more gas sensor cartridge
MultiSense
Free: a MultiSense, stock or built to order
Expansion
Free: differential pressure
Also measures 12 more
Dew PointHeat IndexRelative HumidityIlluminance / LightParticle Count (by size)PM1PM10Total PM / Mass Conc.Barometric PressureEquivalent Continuous Level (Leq)Sound Pressure Level (SPL)Air Temperature
Who measures each parameter
| Parameter | Aethair PRO |  Aethair IAQ |  External |
|---|---|---|---|
| PM2.5 | Built in | Built in | 3 instruments via Thiamis |
Devices
Devices That Cover Cal/OSHA 5141.1
How much of this standard one Aethair monitor covers, followed by the third-party instruments in the sensor catalog that measure its parameters. Each connects to Environet through a Thiamis gateway, which adds whatever the monitor leaves out.
Aethair monitors
Covers it on its own
Solutions
Solutions Judged Against Cal/OSHA 5141.1
Wildfire Air Monitoring
Smoke plumes, black carbon, and community exposure
Article Library
Articles on Cal/OSHA 5141.1
Wildfire Smoke Air Quality Monitoring: Detection & Response
Wildfire smoke monitoring for EHS and public health teams: real-time PM2.5, the AQI 151 respirator trigger, and how to alert workers before smoke arrives.
OSHA Air Quality Standards 2026: PELs & 29 CFR 1910.1000
OSHA air quality standards for indoor and outdoor work: permissible exposure limits, Table Z-1, 29 CFR 1910.1000, and the heat and wildfire smoke triggers.
Questions
Cal/OSHA 5141.1 FAQ
At what AQI does Cal/OSHA's wildfire smoke rule apply?
When the current AQI for PM2.5 is 151 or greater, which the regulation's table equates to 55.5 µg/m³. Above an AQI of 500, respirator use is required.
Can an employer measure PM2.5 on site under section 5141.1?
Yes, with a direct-reading monitor that meets the regulation's Appendix A: it must not underestimate exposure, must measure particles up to 2.5 µm, and must be calibrated and maintained as its manufacturer instructs, with results converted to the AQI.
Is there a federal wildfire smoke standard?
No. California's section 5141.1 is a state rule; there is no federal OSHA wildfire smoke standard.
Monitor Against Cal/OSHA 5141.1
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