Decoding California §5164: Hazardous Substance Storage Rules for Manufacturing Facilities

California's Title 8, Section 5164 of the General Industry Safety Orders hits hard on how manufacturing ops handle hazardous substances. We're talking solvents, acids, paints, and resins commonly stored in production areas, warehouses, or staging zones. This reg, enforced by Cal/OSHA, mandates safe storage to prevent fires, spills, exposures, and those nightmare regulatory citations that can shut down lines.

Scope: When Does §5164 Kick In for Your Plant?

§5164 applies broadly to indoor and outdoor storage of hazardous substances—defined under §5155 as anything with health, flammability, or reactivity hazards. It targets containers over 5 gallons for liquids or 25 pounds for solids in non-original packaging. In manufacturing, this covers everything from 55-gallon drums of epoxy hardeners to pallets of corrosive cleaners.

Exemptions exist for labs under §5191 or portable containers in use. But if your facility mixes, repackages, or holds bulk chemicals, you're in scope. I've walked plants in the Central Valley where overlooking this led to six-figure fines after a minor spill triggered an inspection.

Core Requirements: Containers, Cabinets, and Segregation

1. Approved Containers: All hazardous substances must stay in DOT-approved, tightly sealed containers. No rusty drums or mismatched lids—ever. Label everything per §5144 and GHS standards.
2. Storage Cabinets: Flammable liquids over 25 gallons? Use FM- or UL-listed cabinets. Max 60 gallons per cabinet indoors, 120 outdoors. These aren't optional; they're your fire barrier in a solvent-heavy fab shop.
3. Segregation: Keep incompatibles apart—acids from bases, oxidizers from flammables—at least 20 feet or with barriers. Think warehouse chess: one wrong move, and you've got a reactivity incident.

We've seen §5164 violations spike in electronics manufacturing, where photoresists meet etchants. Pro tip: Map your storage with a compatibility chart from the NFPA 30 or CRC Handbook of Reactive Chemical Hazards.

Indoor vs. Outdoor Storage: Ventilation and Spill Prep

Indoor storage demands 6 air changes per hour ventilation, explosion-proof fixtures, and spill containment holding 10% of the largest container or 10% total volume—whichever's greater. No basements for flammables unless engineered to death.

Outdoor setups get weather protection, diking for spills, and distance from ignition sources (50 feet from buildings for big quantities). In rainy NorCal manufacturing hubs, I've recommended secondary containment pallets that double as forklift bases—practical and compliant.

Both require posted signage, no-smoking zones, and access for emergency responders. Cal/OSHA's interpretation reference manual clarifies gray areas, like aerosol cans counting as pressurized flammables.

Actionable Steps for Manufacturing Compliance

• Audit inventory quarterly: Quantify, classify, and relocate risks.
• Train per §5160: Hands-on sessions on cabinet loading and spill response.
• Integrate with your HazCom program (§5194)—SDS sheets must dictate storage.
• Document everything: Photos, logs, third-party inspections build your defense.

Limitations? §5164 defers to NFPA 30 for quantities over cabinets, so cross-reference. Based on Cal/OSHA data, compliant sites cut incident rates by 40%, but results vary by enforcement and culture. For the full text, hit Cal/OSHA's §5164 page or their consultation service.

Master §5164, and your manufacturing floor stays lean, safe, and inspector-proof. It's not just reg compliance—it's operational armor.