An inside storage room permits the storage of larger quantities of flammable and combustible liquids. However, there are specific requirements for its design and construction that must be followed to protect not only the workers but the general public and the environment.
A storage room for flammable chemicals must be constructed to meet the required fire-resistance rating for its use. It must comply with the following test specifications outlined in the National Fire Prevention Association Standard Methods of Fire Tests of Building Construction and Materials, NFPA 251-1969:
It is recommended that a storage room for flammable liquids be located along an exterior wall because of the danger of explosion. A fire protection system for an inside 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 according to code. The maximum allowable size for a storage room inside a building is 500 square feet. Openings to other rooms or buildings must be provided with non-combustible, liquid-tight, raised sills or ramps, at least 4 inches below the surrounding floor. Approved self-closing fire doors must be used. The room must be liquid-tight where walls join the floor. An open-grated trench inside the room which drains to a safe place might 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 in other exposed properties or exposed portions of the building must be protected as outlined in NFPA Standard for Fire Doors and Windows. Electrical Wiring and equipment located in an inside storage room used for Class I liquids must be approved under Subpart S, Electrical, for Class I, Division 2 Hazardous Locations. If storing only Class II and Class III, electrical wiring shall be approved for general use. An approved ventilation system must be installed.
Since flammable vapors are heavier than air, they hang low to the floor and can accumulate and move toward sources of ignition or other non-compatible chemicals. The ventilation system is vital in preventing flammable vapors from accumulating enough to cause an explosion or liquid fire. Every inside storage room must have either a gravity or mechanical exhausting system which provides a complete change of air within the room at least 6 times an hour. The switch for a mechanical venting system also controls all room lighting and must be located outside the storage room. If gravity venting is provided, the fresh air intake and the exhaust outlet from the room must be on the exterior of the building in which the storage room is located.
Additional Requirements:
Inside every storage room, an aisle at least 3 feet wide must be maintained, allowing for easy movement in the room. This is necessary to reduce the potential for spilling or damaging containers and to provide access for firefighting and a ready escape path from the room if a fire occurs. If wood is used for shelves, it must be at least 1 inch thick and it may also be used for racks, dunnage, scuffboards, floor overlay, etc.. Chemicals are not to be stored on unfinished wooden shelves. Finished metal or high density plastic (polypropylene) is recommended shelving for most chemicals. If wood is used, it must be sealed with a good grade oil based paint, natural or synthetic varnish. Proper segregation of chemicals must be maintained inside the storage room. Incompatible chemicals must be stored at a distance from each other or possible in partitioned areas. Chemicals should be stored at eye level to decrease chance of spilling or breakage and for ease of identification. Labels must be complete, legible and up to date. MSDS information must be available for all chemicals stored. 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 opening into the room. Materials which react with water shall not be stored in the same room with flammable or combustible liquids. Containers over 30 gallons capacity must not be stacked on top of others.
Dispensing of chemicals is by an approved pump or self-closing faucet, or closed piping system. If flammable liquids are dispensed inside the storage room, a pilot light must be installed adjacent to the switch.
Storage Capacity
This depends upon the availability of a sprinkling system and the fire rating of the storage room. One with a fire rating of 2 hours and equipped with sprinklers is allowed to store a greater quantity of chemicals. If fire protection is present in a room that has a 2 hours fire resistance rating, storage allowed is 10 gallons per square foot. If there is no fire protection in this room, 4 gallons of chemicals per square foot is allowed. In a room that has a Fire Resistance Rating of 1 hour, with fire protection, the storage space is decreased 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 fire resistance rating of 1 hour can store 2 gallons of flammable chemicals per square foot.
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