Secondary Containment Requirements: OSHA & EPA

“Secondary containment requirements OSHA” is one of the most-searched phrases in lab chemical safety, but it is also one of the most misleading — OSHA does not have a single, comprehensive secondary-containment regulation the way EPA does. What OSHA actually requires depends on what is being stored and how, and the number most people are looking for (a percentage of container volume) usually comes from a different federal agency’s rule entirely. This guide sorts out which requirement applies to which storage situation, gives the actual regulatory text where a numeric rule exists, and walks through how to size and build containment for a research lab.

What Secondary Containment Is

Secondary containment is a barrier — a tray, curbed room, sump, spill pallet, or diked area — built around a primary chemical or waste container so that if the primary container leaks or ruptures, the released liquid is captured before it reaches a floor drain, groundwater, or an occupied space. It is “secondary” because the container itself is the primary containment; the tray, curb, or dike is the backup.

A compliant secondary containment system generally needs to do three things: hold a defined minimum volume, be built from a material that will not react with or dissolve in the chemical it is meant to contain, and stay free of an uncontrolled drain path (no open valve or crack that lets contained liquid flow straight to a floor drain or outdoors).

The Short Answer: OSHA’s Containment Rules Are Narrow, Not Comprehensive

OSHA regulates workplace safety, not environmental release — so its secondary containment language is limited to a few specific storage configurations, mainly under the flammable and combustible liquids standard, 29 CFR 1910.106. Outside those specific provisions, OSHA does not publish a percentage-based containment formula. Most of what gets casually called an “OSHA secondary containment requirement” is actually an EPA hazardous-waste rule, an EPA oil-spill rule, or a fire-code provision adopted at the state or local level. Getting the source right matters because each one has a different trigger (what you store, how much, and where) and a different capacity formula.

Where OSHA Itself Sets a Containment Number

Diked areas for above-ground flammable liquid tanks

29 CFR 1910.106(b)(2)(vii)(c) requires that where above-ground flammable liquid storage tanks sit inside a diked area, “the volumetric capacity of the diked area shall not be less than the greatest amount of liquid that can be released from the largest tank within the diked area, assuming a full tank” — in practice, the dike must hold 100% of the largest tank’s full capacity. This applies to bulk above-ground tank installations, which is uncommon inside a research lab building but relevant for institutions with an on-site fuel or solvent tank farm.

Outdoor container (drum/tote) storage

For outdoor storage of flammable liquids in containers rather than tanks, 1910.106(d)(6)(iii) takes a different approach: the storage area must be “graded in a manner to divert possible spills away from buildings or other exposures,” or surrounded by “a curb at least 6 inches high.” That is a drainage/diversion requirement, not a percentage-of-volume containment formula.

Where OSHA is silent: indoor bench and cabinet storage

For the situation most labs actually care about — bottles and containers stored on a bench, under a fume hood, or in a flammable-liquid storage cabinet — 1910.106 does not specify a containment volume at all. The obligations that do apply there come from the OSHA Hazard Communication Standard (29 CFR 1910.1200), the Laboratory Standard (29 CFR 1910.1450) requirement to maintain a chemical hygiene plan that addresses safe storage, and the General Duty Clause (Section 5(a)(1) of the OSH Act), which requires employers to address recognized hazards even where no specific standard sets a number. In practice, this is why secondary containment trays under reagent bottles and inside acid/base cabinets are near-universal lab practice even though no OSHA standard explicitly mandates a tray of a specific size for that use case — see chemical storage compatibility and segregation rules and flammable liquid storage cabinet requirements for how those adjacent rules interact with containment.

The EPA Rules That Actually Set the Numbers Most People Are Looking For

RCRA hazardous waste container storage (40 CFR 264.175 / 265.175)

Once a chemical becomes hazardous waste and is held in a central accumulation area under EPA’s Resource Conservation and Recovery Act (RCRA) regulations, secondary containment is federally required, and the sizing rule is the one most EHS professionals actually mean when they say “110% rule”: the containment system must have enough capacity to contain the greater of 10% of the total volume of all containers in the area, or the full volume of the largest container. Containment must also be free of cracks or gaps, sufficiently impervious to prevent leakage, and (if uncovered) able to either drain accumulated precipitation or hold enough additional volume to accommodate it — labs typically satisfy this with a covered area or a sump with a manual drain valve that stays closed by default.

This RCRA requirement is separate from — and stricter than — the rules for a satellite accumulation area (SAA) at the point of waste generation, which is capped at 55 gallons of non-acute waste under 40 CFR 262.15 and does not carry the same explicit containment-sizing requirement, though most institutional waste programs still require a tray or bin under SAA containers as standard practice.

SPCC — oil and petroleum storage (40 CFR 112)

If a facility stores oil (including many petroleum-based lab and equipment fluids) above the SPCC threshold — generally more than 1,320 gallons of aggregate above-ground storage capacity — the EPA’s Spill Prevention, Control, and Countermeasure rule requires secondary containment sized to hold the capacity of the largest single container, plus sufficient freeboard to contain precipitation if the containment is uncovered. Most individual research labs fall well under this threshold, but institutions with bulk fuel storage, generators, or oil-filled equipment at scale need to check aggregate site-wide volume, not just per-container amounts.

Fire Code and NFPA 30 Containment for Indoor Storage Rooms

Where a lab or building keeps flammable or combustible liquids in a dedicated indoor storage room rather than a cabinet, the applicable containment rule usually comes from the locally adopted fire code (most U.S. jurisdictions adopt the International Fire Code or NFPA 1, both of which incorporate NFPA 30 by reference for flammable and combustible liquids) rather than from OSHA or EPA. NFPA 30 requires storage rooms to be built with liquid-tight sills, drains, or graded floors so that a spill stays inside the room and does not reach an exit corridor. Because these are locally adopted codes, the exact containment sizing and construction detail can vary by jurisdiction — the authority having jurisdiction (typically the local fire marshal) is the definitive source for a specific building.

How to Size Secondary Containment for a Lab: A Practical Approach

Because no single number covers every situation, size containment to the strictest rule that actually applies to the specific storage location:

Bench-top and cabinet storage of chemicals (not yet waste): no OSHA-mandated volume, but standard practice is a tray or bin sized to hold the full contents of the largest bottle stored in it, to satisfy the Chemical Hygiene Plan’s general duty to control spill risk.
Hazardous waste containers in a central accumulation area: size to the RCRA formula — the greater of 10% of total container volume in the area, or 100% of the largest single container.
Outdoor drum or tote storage (non-waste, flammable liquids): follow 1910.106(d)(6)(iii) — graded drainage away from the building, or a curb at least 6 inches high.
Above-ground bulk tanks: follow 1910.106(b)(2)(vii)(c) — dike capacity at least equal to the largest tank’s full volume.
Bulk oil or petroleum storage over the SPCC threshold: follow 40 CFR 112 — capacity for the largest single container plus precipitation freeboard.
Indoor flammable liquid storage rooms: follow the locally adopted fire code (NFPA 30 via the IFC or NFPA 1) — confirm sizing with the local fire marshal or the institution’s fire protection engineer.

Construction and Material Requirements

Regardless of which rule sets the size, a secondary containment system needs to meet the same basic construction criteria to actually function:

Chemical compatibility: the tray, sump, or dike liner must not react with, dissolve in, or be permeated by the chemical it is meant to hold — polyethylene works for most acids and bases but is unsuitable for many organic solvents; check compatibility the same way you would for gloves or storage containers (see chemical-resistant glove selection for the same compatibility logic applied to PPE).
No uncontrolled discharge path: any drain valve on a containment sump must default closed and require a deliberate action to open — an open or leaking valve defeats the containment entirely and is a common inspection finding.
Structural integrity: no cracks, corrosion, or gaps at seams; inspect regularly, especially where corrosive chemicals are stored — see corrosive chemicals in the lab for handling and storage hazards that accelerate containment degradation.
Precipitation management for outdoor/uncovered containment: either a cover that keeps rain out, or enough reserve capacity above the container-volume requirement to hold accumulated precipitation between inspections.

Common Compliance Mistakes

Citing “the OSHA 110% rule.” There is no such OSHA rule. The 10%-of-total/100%-of-largest formula is an EPA RCRA hazardous waste requirement (40 CFR 264.175/265.175), not an OSHA standard — citing it as OSHA in an inspection response or SOP is a citation error, even though the practical containment tray itself may be identical.
Leaving a sump drain valve open “for convenience.” This is one of the most common EPA and fire-inspector findings — an open valve routes contained liquid straight to a floor drain, negating the containment entirely.
Undersizing containment for mixed-volume storage. When several different container sizes share one containment area, the requirement is driven by whichever is larger — 10% of the total, or the single largest container — not by an average.
Assuming a spill kit substitutes for engineered containment. A chemical spill kit is a response tool for after a release happens; it does not satisfy a secondary containment requirement, which is a passive, always-in-place engineering control.
Ignoring aggregate volume across a room. RCRA and SPCC thresholds are both based on aggregate volume across a storage area or site, not per-container amounts — a room full of small containers can trigger a containment requirement that no single container would.

Frequently Asked Questions

Does OSHA require secondary containment for every chemical storage area?

No. OSHA’s own numeric containment requirements are limited to above-ground flammable liquid tanks (1910.106(b)(2)(vii)(c)) and outdoor flammable liquid container storage (1910.106(d)(6)(iii)). For most indoor bench and cabinet storage, containment is driven by the Chemical Hygiene Plan’s general duty to control hazards rather than an explicit OSHA volume formula.

What is the “110% rule” people mention for secondary containment?

It is most often a loose paraphrase of the EPA RCRA hazardous waste container storage rule (40 CFR 264.175/265.175), which requires containment capacity equal to the greater of 10% of the total container volume in the area or 100% of the largest single container’s volume — not an OSHA standard, and not a flat 110% figure written into the regulation itself.

Do satellite accumulation areas need secondary containment?

The federal satellite accumulation rule (40 CFR 262.15) does not carry the same explicit containment-sizing requirement as a central hazardous waste accumulation area, but most institutional environmental health and safety programs still require a tray or bin under satellite containers as standard practice, both for spill control and because state rules can be stricter than the federal floor.

Does a fume hood or storage cabinet count as secondary containment?

Not by itself. A cabinet or fume hood controls exposure and fire risk; a spill tray, sump, or lined shelf inside it is what actually provides liquid containment if a container leaks.

How often should secondary containment be inspected?

There is no single federal inspection interval that applies to every containment type; RCRA requires that hazardous waste container areas be inspected weekly for leaks and containment condition, and most institutional EHS programs apply a similar weekly-to-monthly cadence to chemical storage containment as a matter of policy even where not explicitly mandated.