California Senate Bill 883 (SB 883), commonly referred to as the Preventing Chemical Explosions Act, has officially become law. Governor Gavin Newsom approved the measure on September 27, 2026, and it was filed as Chapter 658, Statutes of 2026. The law responds to concerns about thermal runaway reactions and other explosion hazards at facilities that store or use reactive chemicals, with particular attention to methyl methacrylate (MMA).
SB 883 establishes new permitting, siting, emergency-planning, inspection, and accidental-release-prevention requirements. The law does not prohibit the manufacture, storage, or use of reactive chemicals or MMA. Instead, it creates additional safeguards for covered facilities and directs regulators to develop further requirements.
Which Facilities May Be Covered?
SB 883 establishes requirements for both existing and new “reactive chemical storage” facilities, although the applicable definition and obligations differ depending on the provision.
For purposes of the new-facility building permit requirements, a “reactive chemical storage facility” generally means a stationary source with a process involving a reactive substance. The permitting requirements apply to a proposed new facility with the potential for an explosion, including, but not limited to, an explosion resulting from a thermal runaway reaction, that could cause injury or death beyond the facility’s property boundary.
For the requirements applicable to existing facilities, SB 883 addresses stationary sources that store and use methyl methacrylate (MMA). The legislation also amends California’s Accidental Release Prevention (CalARP) statute to add MMA to the definition of a “regulated substance.” However, the California Environmental Protection Agency (CalEPA) must establish the applicable state threshold quantity for MMA through regulation.
Accordingly, SB 883 should not be viewed solely as an MMA regulation. Facilities should assess which provisions apply based on their chemical processes, reactive hazards, potential offsite consequences, and whether a proposed project constitutes a new reactive chemical storage facility. Facilities that store or use MMA should separately evaluate the new CalARP provisions and monitor CalEPA’s establishment of the MMA state threshold quantity.
Building-Permit Criteria for Covered New Facilities
The permit provisions apply when a new facility has the potential for an explosion including, but not limited to, an explosion caused by a thermal runaway reaction that could injure or kill a person beyond the facility’s property boundary. The building permit criteria for a new “reactive chemical storage facility” are described below.
- The proposed facility must have a backup cooling system or other contingency system for reactive chemical storage that is reviewed and approved by the applicable Certified Unified Program Agency (CUPA).
- The proposed facility may not be adjacent to a home. Because the statute does not establish a numerical separation distance for “adjacent,” project proponents should engage the local land-use authority and CUPA early.
- The city council or county board of supervisors must provide public notice and an opportunity to comment before approving the building permit.
- After approval, the local government must notify the California Governor’s Office of Emergency Services (Cal OES) and the Office of Environmental Health Hazard Assessment (OEHHA).
Additional Regulatory and Emergency-Planning Requirements
SB 883 also creates broader oversight obligations. CUPAs must conduct routine inspections of covered reactive chemical storage facilities with MMA at least every three years and report inspection results to specified state agencies. Facilities should confirm the inspection frequency and reporting process with their CUPA as implementation guidance is issued. Local emergency plans must identify the lead department or agency for hazardous-materials response when those plans are next revised, improving clarity during a chemical incident.
The legislation also requires OEHHA to consider reactive chemical storage facilities as a factor when identifying disadvantaged communities for purposes of existing California law
What Regulated Businesses Should Do Now
Facilities that store or use reactive chemicals, and particularly facilities that handle MMA, should consider evaluating how SB 883 affects their operations. Key considerations include:
- Determine whether the facility meets the statutory definition of a reactive chemical storage facility.
- For proposed new facilities, evaluate the new building-permit requirements, including explosion potential, contingency-system requirements, siting, and public participation.
- Prepare for CUPA inspections at least once every three years if the facility falls within the reactive chemical storage facility definition.
- For facilities storing or using MMA, evaluate potential CalARP applicability in light of MMA’s addition as a regulated substance and monitor CalEPA’s rulemaking establishing the state threshold quantity.
- Do not treat the reactive-chemical provisions and the MMA provisions as interchangeable. SB 883 establishes requirements for reactive chemical storage facilities while separately amending CalARP to specifically address MMA
- Track CalEPA rulemaking for the MMA threshold quantity and related CalARP implementation requirements.
How Trinity Can Help
SB 883 creates immediate planning considerations while leaving important implementation details to state and local agencies. Facilities that store or use MMA or other reactive substances should begin reviewing their operations now rather than waiting for permit activity or agency outreach. Trinity Consultants can help facilities conduct applicability reviews, evaluate reactive hazards and offsite consequences, assess contingency systems, prepare for CUPA inspections, and determine whether CalARP or related emergency-planning updates may be required. To discuss your business obligations and readiness, contact Principal Consultant Charles C. Lee, Ph.D.
