Flammable Liquids: Guidelines and Best Practices for Safe Storage

An inventory revealed overlooked hazards in flammable storage cabinets. Here’s what safety managers need to know about cabinet standards, liquid categories, storage limits, and inspection best practices to keep facilities safe and compliant.

• By Tom Burgess
• Jul 16, 2025

In this story, we’ll examine a flammable liquids inventory approach and the initial findings from that approach. Using a streamlined digital process via Google Forms, chemical data was collected, including the substance name, manufacturer, physical state, container type and size, and departmental location. Each flammable storage cabinet was labeled using a department abbreviation (e.g., “M” for Maintenance) followed by a sequential number. The resulting inventory was cross-referenced with the facility’s Safety Data Sheet (SDS) library to ensure all relevant SDSs were available. 

However, the inventory process also uncovered serious safety oversights. Many cabinets had not been inspected in some time. A few concerning issues included: Issues included: items stored on top of cabinets; leaking containers; cardboard boxes and other combustible materials stored inside; a cabinet that contained a hand torch and spark lighter — introducing potential ignition sources; and improper cabinet sizing for the chemical containers, increasing spill risk. 

These findings highlighted the need for stronger adherence to safety guidelines and regular inspections. 

Purpose and Construction Standards of Flammable Storage Cabinets 

Flammable storage cabinets are designed to minimize fire hazards by safely containing flammable liquids. Their construction and use are regulated by OSHA and the National Fire Protection Association (NFPA). Key requirements include: 

• Cabinets must be constructed of at least 18-gauge sheet metal, be double-walled, and have a 2-inch raised door sill to contain spills. 

• Wood cabinets are acceptable if they meet specifications outlined in OSHA Standard 1910.106. 

• A conspicuous label reading “FLAMMABLE – KEEP FIRE AWAY” must be affixed. 

• Cabinets must typically remain sealed (non-vented) to prevent oxygen intrusion, which could fuel a fire. 

• In states following the International Fire Code (IFC), self-closing doors may be required. 

Understanding Flammable Liquid Categories 

Since the 2012 update to OSHA Standard 1910.106, flammable and combustible liquids are grouped into four categories based on flashpoint and boiling point. These align with the Globally Harmonized System (GHS), which categorizes flammable liquids in Section 2 of the SDS as shown in the chart, “Four Flammable and Combustible Liquids Categories.” 

Table 1: Four Flammable and Combustible Liquids Categories 

These categories are in line with the Globally Harmonized System (GHS) for labeling chemicals. The GHS Flammable Liquid category will be listed within Section 2 of the SDS.   

The use of flammable cabinets is mandatory when storing 25 gallons or more of Category 1 flammable liquids. Common facilities that require such storage include industrial plants, laboratories, and medical centers. 

Storage Limits and Container Guidelines 

OSHA 1910.106 limits cabinet storage to 60 gallons for Category 1, 2, or 3 flammable liquids and 120 gallons for Category 4 flammable liquids. 

Maximum allowable container sizes vary depending on the liquid category and container material (e.g., metal, plastic, glass). See Table 2, which outlines the type of container and maximum container size based on the Category of liquid being stored. 

Table 2: Maximum Container Size by Container Type for Each Category 

Common flammable liquids include fuel, paint thinners, solvents and degreasers, paints, chemicals in aerosol cans, alcohols (such as isopropyl alcohol, ethanol and methanol), acetone, xylene and toluene. 

Prohibited Storage and Best Practices 

Flammable cabinets should not be used to store incompatible substances such as acids, bases, or other corrosives. These are typically identified as fuels, paint thinners, solvents and degreasers, paints, chemicals in aerosol cans, alcohols (such as isopropyl alcohol, ethanol and methanol), acetone, xylene and toluene 

Additionally, flammable cabinets should remain free of paper, cardboard, wood, and cabinet tops should be kept clear of materials to avoid providing fuel for any unforeseen fire events.  

Inspection and Maintenance Protocols 

Incorporating regular cabinet inspections into your safety program is essential. While OSHA doesn’t mandate a specific frequency, monthly or quarterly checks are recommended. Develop a checklist that includes: 

• Exterior: Check for rust, dents, and legible labeling. 

• Doors and Seals: Ensure latch functionality and tight door seals. 

• Interior: Inspect shelving, look for leaks or damaged containers, and verify labeling. 

Consistent documentation will support audits and foster accountability.   

Training and Compliance 

Staff must be trained on proper cabinet use, inspection protocols, and what can—and cannot—be stored within. Maintaining cabinets in good condition and ensuring they're free from spills, leaks, and improper content helps prevent incidents and ensures regulatory compliance. 

This article originally appeared in the July/August 2025 issue of Occupational Health & Safety.