Ask a California school district how it decides the air in a smoke-damaged campus is safe for children, and the honest answer is on the Department of Education’s own recovery page: “There is no indoor air quality standard.” No state number to test against, no pass-fail line to clear. Districts reopened after the January 2025 fires on judgment, county guidance, and exposure control — and the statute California just enacted for wildfire smoke does not change that for schools. AB 1642 (Chapter 239, signed September 15, 2026) builds an interim clearance standard for houses. For schools, it orders a document: advisory, nonregulatory guidance from the Department of Toxic Substances Control, due July 1, 2028. Facility leaders planning reoccupancy work between now and then need to know exactly what exists today, what the 2028 document will and will not be, and why the residential number cannot simply be borrowed for a campus.
What AB 1642 actually orders for schools
Health and Safety Code section 25402.6 directs DTSC, in collaboration with the Department of Education and other state agencies, to develop advisory, nonregulatory guidance for schools — “local educational agencies,” meaning schools, districts, charter schools, and county offices of education — no later than July 1, 2028. The statute lists what the guidance must contain: the balance between protecting the health of pupils, staff, and community members and reopening schools as expeditiously as possible to promote stability; suggested best practices for pre- and post-remediation testing and for remediation and restoration, including how to find, evaluate, and select appropriately licensed personnel; information on wildfire hazards and how to interpret results when deciding to close or reopen, and how to reduce exposure and recontamination; and information on which federal, state, and local entities can provide expertise, and what emergency funds exist.
Read the label twice: advisory, nonregulatory. The guidance will describe a method. It will not set a clearance standard a district can pass or fail, and its adoption is exempt from the Administrative Procedure Act process that a regulation would require.
The house number is not a school number
The same act does create a numeric clearance — for residences. Section 25402.3 sets an interim standard “for the purposes of determining clearance for human occupancy for residential properties located within a wildfire impact zone,” covering wildfire-caused lead and asbestos only: interior lead dust not to exceed the federal action levels in 40 CFR 745.227(e)(8)(viii) — 5 µg/ft² on floors, 40 on interior window sills, 100 on window troughs — with asbestos handled by compliance with the Cal/OSHA construction standard and the federal asbestos NESHAP. It operates from January 1, 2027, when the act takes effect, until DTSC’s regulations and the state’s indoor-air guidance arrive in late 2028 and 2029. By its own words it does not name schools. A district that adopts the residential dust-lead ceiling as its campus criterion is making a local policy choice, not following a state school standard — and should minute it as exactly that.
How reoccupancy was actually decided in 2025
The published record of the last recovery is a patchwork of state event guidance and county practice, and it is the real predecessor the 2028 document will land on.
The Department of Education’s standing recovery FAQ — still current at its August 25, 2026 review — is the closest thing to a statewide reoccupancy protocol: once outdoor air is satisfactory, ventilate facilities, classrooms, and offices for at least 24 hours; replace HVAC filters, at least MERV 8 and preferably higher if the system can take it; sweep ash gently; use HEPA vacuums; wet-clean hard floors, desks, and bookcases; clean toys, athletic equipment, and drinking fountains exposed to settled ash; and do not use ozone generators to deodorize, because ozone can form formaldehyde and ultrafine particles. On the safety question itself, the FAQ’s line is the one quoted above: there is no indoor air quality standard. During a smoke event, the decision tool is outdoor air — closure and activity modification are local decisions driven by air-quality measurements, filtration, and site conditions, under the state’s “Get Smart about Wildfire Smoke” guidance and OEHHA’s AQI-based school guidance.
Los Angeles County Public Health filled the post-fire gap for reopened schools in its March 17, 2025 FAQ: inspect and clean outdoor areas, playgrounds, and equipment; keep filtration at MERV 13 or higher and close windows and doors as needed; watch wind and air quality and keep people indoors on bad days; and use remediation experts as needed, especially when considering soil or other environmental testing — with the advice keyed to distance from debris that the phased removal operations had not yet cleared. Pasadena Public Health, responding to the county soil study in April 2025, added the soil track: DTSC’s soil screening level of 80 parts per million for lead — a screening value that indicates a need for more evaluation, not itself a cleanup order — and, for schools and early-childhood centers in the mapped areas, a strong recommendation for qualified-professional soil testing, with exposed-soil fields and school gardens closed, track-in controls at entries, handwashing, and daily wet-mopping until results or remediation were in hand.
Los Angeles Unified’s environmental health office assessed 11 schools in and around the Palisades area: soil, air, and dust sampling found no significant contamination or health risks at the standing schools, with minor arsenic and lead exceedances in isolated samples mitigated or judged minimal. The three burned schools stayed in a separate remediation track — thousands of tons of soil removed at one campus, lead-contaminated soil still being removed at another. Standing schools were handled with cleaning, filtration, and monitoring; burned schools were construction projects. The distinction is the whole pattern.
What a facility leader does with a two-year gap
First, stop waiting for the number. The document due July 1, 2028 is guidance about balance, testing practice, personnel selection, and funding — written for the decisions districts already make. A district that builds its reoccupancy file now, on the county pattern, will find the 2028 guidance describes what it already does.
Second, write the file like a clearance file even though no clearance standard exists: the sampling you commissioned and who performed it, the results and the comparison values you chose and why, the cleaning and filtration steps taken, and the reopening decision with its basis. The residential side of this same statute pair just made exactly that file legally operative for houses — the Restoration Intel desk’s read of the clearance standard, the presumption, and the insurer duties is The Standing House Gets a Clearance File. Schools were deliberately left to guidance; the discipline transfers even where the standard does not.
Third, treat ventilation and filtration as the standing control, not the emergency one. The through-line from the state FAQ to the county guidance is MERV-rated filtration, HEPA cleaning, and wet methods — the same plant-level thinking this desk applies to healthcare ventilation in What Is ASHRAE Standard 170? and to sampling evidence in Air Sampling During Healthcare Construction: a measurement is only as good as the documented method behind it, and “no standard exists” is a reason to document more carefully, not less.
Sources: AB 1642 (Chapter 239, Stats. 2026), Health and Safety Code sections 25402.3 and 25402.6; California Department of Education wildfire recovery FAQ (reviewed August 25, 2026) and air-quality guidance for schools; Los Angeles County Public Health school FAQ, March 17, 2025; Pasadena Public Health schools and early-childhood guidance, revised April 15, 2025; LAUSD school assessment summary, Los Angeles County Public Health.