Washington updates smoke AQI references without changing PM2.5 triggers

October 7, 2026

Washington updated the Air Quality Index references in its wildfire-smoke rules effective May 16, 2025. L&I’s status page expressly says the requirements based on PM2.5 concentrations did not change. The amendment aligns the corresponding AQI values with EPA’s revised mapping.

APT’s Washington wildfire smoke AQI update tracker record records the updated AQI references alongside the unchanged concentration requirements.

The reference changed while the exposure basis remained

The permanent rulemaking order was filed on April 15, 2025. L&I explains that EPA had changed AQI breakpoints on May 6, 2024. Updating the AQI references allows employers using the index to relate it to the state rule’s concentration-based requirements.

PM2.5 concentration is a mass-per-volume measurement. AQI is a unitless index. Changing the index value associated with a concentration does not, on its own, establish that the workplace concentration threshold has been reduced.

The underlying rules use hourly average PM2.5 concentrations. Their protective measures need to be matched to that basis, including when the employer uses an approximate corresponding AQI value for implementation.

Check displayed tables and supervisor instructions

APT’s practical interpretation is to review smoke plans, posted instructions and any software or reference sheets that display AQI action points. An old AQI reference could lead a supervisor to apply the wrong action tier even where the underlying concentration requirements were carried forward correctly.

The permanent workplace rules remain the source for coverage, action tiers and required protections. This update does not establish a new universal workplace particulate limit or remove the need to identify the applicable agriculture or general-workplace provisions.

Find related developments in the industrial hygiene regulatory tracker.