An indoor storage room allows large quantities of flammable and combustible liquids to be stored. However, there are specific requirements for its design and construction that must be followed to protect not only workers but the general public and the environment.

A flammable chemical storage room must be constructed to meet the fire resistance rating required for use. It must meet the following test specifications outlined in the National Fire Prevention Association’s Standard Methods for Fire Testing of Materials and Building Construction, NFPA 251-1969:

• It is recommended that a flammable liquid storage room be located along an exterior wall due to the danger of explosion.
• A fire protection system for an indoor storage room is a sprinkler system, water spray, carbon dioxide, or other system that has been approved by local fire authorities.
• If an automatic sprinkler system is present, it must be designed and installed in accordance with code.
• The maximum size allowed for a storage room within a building is 500 square feet.
• Openings to other rooms or buildings should be provided with liquid-tight, noncombustible raised thresholds or ramps, at least 4 inches below the surrounding floor.
• Approved self-closing fire doors must be used.
• The room should be liquid tight where the walls meet the floor.
• An open screen trench into the room that drains to a safe location could be an acceptable alternative to the sill or ramp. If a lot of flammable liquids are transferred in and out of the room using hand trucks, this might be preferable.
• Windows on other exposed properties or exposed parts of the building must be protected as described in the NFPA Standard for Fire Doors and Windows.
• Electrical wiring and equipment located in an indoor storage room used for Class I liquids must be approved under Subpart S, Electrical, for Class I, Division 2 hazardous locations. If you store only Class II and Class III, the wiring electrical must be approved for general use.
• An approved ventilation system must be installed.

Since flammable vapors are heavier than air, they hang close to the floor and can collect and travel to sources of ignition or other non-compatible chemicals. The ventilation system is vital to prevent flammable vapors from building up enough to cause an explosion or liquid fire. Each indoor storage room must have a mechanical or gravity exhaust system that provides a complete change of air within the room at least 6 times per hour. The switch for a mechanical ventilation system also controls all lighting in the room and should be located outside the storage room. If gravity ventilation is provided, the room’s fresh air inlet and exhaust outlet should be on the outside of the building in which the storage room is located.

Additional requirements:

• Within each storage room, a hallway should be maintained at least 3 feet wide, allowing for easy movement in the room. This is necessary to reduce the possibility of containers being spilled or damaged and to provide access for fire fighting and a ready escape route from the room if a fire occurs.
• If wood is used for the shelves, it must be at least 1 inch thick and can also be used for shelving, stowage, scuff boards, floor covering, etc.
• Chemicals should not be stored on unfinished wooden shelves. Finished metal or high-density plastic (polypropylene) shelves are recommended for most chemicals. If wood is used, it should be sealed with a good quality oil-based paint, natural or synthetic varnish.
• Adequate chemical product segregation must be maintained within the storage room. Incompatible chemicals should be stored at a distance from each other or possibly in divided areas.
• Chemicals should be stored at eye level to reduce the possibility of spillage or breakage and to facilitate identification.
• Labels must be complete, legible, and up-to-date.
• MSDS information must be available for all stored chemicals.
• At least 1 portable fire extinguisher with a rating of not less than 12-B units must be located outside the storage room, no more than 10 feet from the door that opens into the room.
• Materials that react with water should not be stored in the same room with flammable or combustible liquids.
• Containers over 30 gallon capacity should not be stacked on top of one another.

Chemicals are dispensed using an approved pump, self-closing faucet, or closed plumbing system. If flammable liquids are dispensed within the storage room, a pilot light should be installed next to the switch.

Storage capacity

• This depends on the availability of a sprinkler system and the fire rating of the storage room. One with a 2 hour fire rating and equipped with sprinklers can store more chemicals.
• If there is fire protection in a room that has a 2 hour fire rating, the allowed storage is 10 gallons per square foot.
• If there is no fire protection in this room, 4 gallons of chemicals are allowed per square foot.
• In a room that has a fire resistance rating of 1 hour, with fire protection, the storage space is reduced to 150 square feet.
• The amount of flammable chemicals that can be kept in this room is 5 gallons per square foot.
• A room that has no fire protection and a 1-hour fire resistance rating can store 2 gallons of flammable chemicals per square foot.