Flammable and Combustible Liquids: What OSHA's 1910.106 Actually Requires from Small Businesses

Walk through most small shops, auto service centers, print operations, or janitorial supply rooms and you will find flammable and combustible liquids stored in ways that compliance officers flag immediately: open containers sitting on open shelves, safety cans wedged between cardboard boxes, or five-gallon plastic jugs of solvent stacked in a storage room with no spill containment. These are not exotic violations. They are the everyday storage habits that OSHA's 29 CFR 1910.106 was written to address, and they generate citations across industries that do not think of themselves as particularly chemical-intensive.

If your business uses gasoline, acetone, mineral spirits, lacquer thinner, isopropyl alcohol, diesel, or common cleaning solvents, 1910.106 applies to you. Understanding what it actually requires — and where small businesses most commonly fall short — is the first step toward a compliant, fire-safe storage program.

The Classification System That Drives Everything

Every requirement in 1910.106 flows from how the liquid is classified. Flammable liquids have a flash point below 100°F — the temperature at which they release enough vapor to ignite. Class I-A covers materials like diethyl ether (flash point below 73°F, boiling point below 100°F). Class I-B includes gasoline and acetone. Class I-C includes turpentine and similar materials in the 73–100°F flash-point range. Combustible liquids have flash points at or above 100°F; Class II covers diesel and kerosene (100–140°F range), while Class III covers heavier oils.

This classification determines how much you can store in a given area, what container types are permitted, whether you need a dedicated storage room, and what ventilation is required. A business storing only Class II combustibles has more flexibility than one storing Class I-A flammables — but both are subject to the standard and both will draw citations if storage practices are ignored.

Container Requirements and Quantity Limits

The standard sets specific container size limits by liquid class and material. For Class I-A liquids, glass or approved plastic containers are limited to one pint. Class I-B and I-C liquids can be stored in glass or plastic containers up to one quart. Metal containers — including approved safety cans — can hold up to five gallons for Class I and II liquids. Safety cans, defined in 1910.106(a)(26) as approved containers with spring-closing lids and flash-arresting screens, are the preferred storage option for most general industry use.

The inside storage limit that surprises many businesses: without an approved storage room or flammable storage cabinet, you are limited to 25 gallons of Class I-A, 120 gallons of Class I-B and I-C, and 660 gallons of Class II liquids in a single fire area. An auto shop with several containers of acetone, safety cans of gasoline, and a drum of mineral spirits may already be over the applicable threshold without knowing it.

Flammable Storage Cabinets: What They Actually Do

Many small businesses treat approved flammable storage cabinets as a catch-all compliance solution. They are not. Cabinets listed under UL Standard 1275 are tested to withstand a ten-minute fire exposure without allowing internal temperature to exceed 325°F — they buy time during a fire, they do not eliminate the hazard.

Under 1910.106(d)(3), a cabinet cannot hold more than 60 gallons of Class I or II liquids. The bottom must be liquid-tight to at least two inches to contain spills. Vent openings must be sealed with bungs unless the cabinet is specifically designed for use in a ventilated system — using the cabinet as an exhaust point defeats its fire rating. Cabinets must be kept away from ignition sources and should never be positioned near electrical panels, furnaces, or welding areas.

Inside Storage Rooms and Ventilation

When quantities exceed what cabinets and general floor storage allow, 1910.106(d)(4) requires an inside storage room constructed to specific fire-resistance standards. Key requirements include a minimum of six air changes per hour with exhaust taken from floor level, wiring rated for Class I hazardous locations when Class I liquids are present, self-closing fire doors, liquid-tight raised sills or ramps at doorways, and automatic sprinklers for rooms over 150 square feet storing Class I liquids.

Floor-level exhaust is one of the most commonly cited deficiencies. Flammable vapors are heavier than air and settle rather than rise — a standard HVAC system drawing from ceiling height does nothing to clear them. Dedicated explosion-proof exhaust fans positioned low on an exterior wall are the correct solution.

Building a Compliant Program

The businesses cited for 1910.106 violations are almost never the ones that thought carefully about storage. They are the ones that accumulated containers over time, made assumptions about compliance, and never compared their inventory against the standard.

Start by cataloguing every flammable and combustible liquid on-site and classifying each by flash point. Confirm that containers are approved types with proper lids, correctly labeled, and within the permitted size limits. Calculate total quantities by class and compare against inside storage thresholds to determine whether you need additional cabinets or a dedicated room. Verify that existing cabinets carry a UL 1275 listing and are located away from ignition sources. Check that any enclosed storage area has adequate floor-level ventilation. Train employees on safe transfer, spill response, and proper container use — and document it.

A focused review of your storage practices, followed by a few targeted purchases if gaps exist, closes most 1910.106 compliance issues without major expense. The standard is specific, but the underlying requirements are not complicated. What catches businesses is not the complexity — it is the assumption that the way things have always been stored must be acceptable.