how to store & use flammable liquids - part 2
- ASTM F 852, Standard Specification for Portable Gasoline Containers for Consumer Use
- ASTM F 976, Standard Specification for Portable Kerosene and Diesel Containers for Consumer Use
- ANSI/UL 1313, Standard for Nonmetallic Safety Cans for Petroleum Products
- ANSI/UL 30, Standard for Metal Safety Cans
- ANSI/UL 1314, Standard for Special Purpose Metal Containers
- FM Global Approval Standard for Safety Containers and Filling, Supply, and Disposal Containers — Class Number 6051 and 6052
Note in the table that plastic containers are not NOT ALLOWED to be used with flammable liquids (‘NP’= not permitted), unless the liquids are water miscible. We also covered this in our first post on flammable liquid and storage.
There are three primary storage options available with flammable liquids:
- In portable storage cabinets
- In a storage room
- Outside the building (either in the open, an attached or detached building, or storage locker)
During operations when flammable liquids need to be used, a small supply can be located outside of “approved” storage in one fire area per OSHA 1910.106.
However, it is a best practice to have all flammable liquids stored with one of these methods whenever possible. Note that safety cans (UL/FM approved) with appropriate dispensing equipment should always be used for dispensing from portable containers.
Outside the building
Often the easiest and least expensive options are to store flammable (and combustible) liquids outside the building. Outside storage of course provides natural ventilation; however, there are climate (i.e. temperature) and security concerns. This of course depends on whether the flammable liquid can be stored safely outside.
The material safety data sheets and other information from the manufacturer should be consulted before this is done. Once it has been determined that it is safe to do so, NFPA publishes the following chart with regard to distances, quantities, etc.:
Additional controls include the following:
- The area should slope away from the building or be diked in the event of a spill so that the liquid does not flow toward the building.
- The storage should be secured (e.g. fenced)
- It needs to be stored in such a way that fire apparatus can have easy access to it.
- The distances between the outdoor storage and an occupied building will vary depending on several factors- the fire wall barrier rating (construction of the wall); fire protection of the building and other factors.
An efficient and cost effective means to portable storage may be storage cabinets. Cabinets are not without hazards, which include:
- Risk of spills
- Possible tip-over or blockage of egress
- Maintenance of vent and grounding integrity
- Condition of floor surfaces under the cabinet that may make the cabinets unstable
Not any “ordinary” cabinet can be used, however. NFPA 30, 9.5.3 specifies that the cabinets must meet one of four sets of specifications:
- Storage cabinets designed and constructed to limit the internal temperature at the center of the cabinet and 1 in. (25 mm) from the top of the cabinet to not more than 325°F (163°C), when subjected to a 10-minute fire test that simulates the fire exposure of the standard time/temperature curve.
- Metal storage cabinets constructed in the following manner shall be acceptable:
- The bottom, top, door, and sides of the cabinet shall be at least No. 18 gauge sheet steel and shall be double-walled, with 11/2 in. (38 mm) air space.
- Joints shall be riveted, welded, or made tight by some equally effective means.
- The door shall be provided with a three-point latch arrangement, and the door sill shall be raised at least 2 in. (50 mm) above the bottom of the cabinet to retain spilled liquid within the cabinet.
- Wooden cabinets constructed in the following manner shall be acceptable:
- The bottom, sides, and top shall be constructed of exterior grade plywood that is at least 1 in. (25 mm) thick and of a type that will not break down or delaminate under fire conditions.
- All joints shall be rabbetted and shall be fastened in two directions with wood screws.
- Where more than one door is used, there shall be a rabbetted overlap of not less than 1 in. (25 mm).
- Doors shall be equipped with a means of latching, and hinges shall be constructed and mounted in such a manner as to not lose their holding capacity when subjected to fire exposure. (e) A raised sill or pan capable of containing a 2 in. (50 mm) depth of liquid shall be provided at the bottom of the cabinet to retain spilled liquid within the cabinet.
- Listed cabinets (e.g. Underwriters Laboratories) are acceptable, provided they meet the provisions of section #1.
If fire cabinets are used for flammable liquids storage, the storage must meet the following requirements:
- Less than 120 gal (454 L) of Class I, Class II, and Class IIIA liquids shall be stored in a storage cabinet. Of this 120-gal total, not more than 60 gal (227 L) shall be Class I and Class II liquids.
- Not more than six storage cabinets shall be located in any one fire area. (three for non-sprinklered buildings).
- Storage cabinets shall be marked in conspicuous lettering: "FLAMMABLE — KEEP FIRE AWAY."
- If the volume of storage is more than the above guidelines, than an approved flammable storage room should be constructed.
One question that often arises is whether cabinets need to be vented. Per NFPA 30, the simple answer is no. The Apex in 9.5.4 explains that venting of storage cabinets has not been demonstrated to be necessary for fire protection purposes, and could compromise the ability of the cabinet to adequately protect its contents against fire because cabinets are not generally tested with any venting.
However, it is recognized that some jurisdictions might require storage cabinets to be vented and that venting can also be desirable for other reasons, such as health and safety. In such cases, means of accomplishing this can include thermally actuated dampers on the vent openings or sufficiently insulating the vent piping system to prevent the internal temperature of the cabinet from rising above that specified.
The details of the requirements for this type of storage can be found in NFPA 30, Chapter 9 (beginning with 9.5). There are additional special occupancy requirements that must be considered.
Flammable Liquid Storage Room
When the above two options do not work, an approved liquid storage room may be an option. The quantities allowed will depend on the nature of the occupancy, whether the room is an inside storage room, cutoff room, or attached building, and the local authority having jurisdiction (AHJ).
The primary requirements (in a very concise format) for an inside storage room are as follows:
- Interior walls and ceiling should have a 3 hr. fire resistance. The exterior wall should have accessibility for fire-fighting operations through windows, access panel, or lightweight noncombustible wall panels.
- Explosion venting capability through lightweight wall assemblies or through windows designed for this purpose (NFPA 68 Guide for Explosion Venting has additional information.
- All openings in interior walls should be protected by automatic 3-hour rated fire doors.
- For containment (to prevent fuel spread), liquid-tight curbs should be provided and ramps at least 6” in height (or higher if the amount of liquids would fill the room to a higher level than this) across the width of the opening. An open-grilled trench on the inside face which drains to a safe location is also an option.
- Wall scuppers, trapped floor drains, or trapped trench drains terminating in a safe location. The drains should be sized to effectively handle the expected sprinkler discharge.
- Electrical wiring and equipment suitable for Class I Division 2 locations, except within three feet of a flammable dispensing nozzle area where it should be suitable for Class I, Division I.
- Grounding and bonding facilities for containers at any dispensing location for Class I liquids.
- Mechanical ventilation of 1CFM/ft2 of floor area but not less than 150CFM. Fan(s) should have blades of non-sparking material with exhaust pickup(s) taken within 6 in. of the floor.
- The room should be equipped with an approved fire suppression system (approved by the Authority Having Jurisdiction, or “AHJ”) or fire sprinklers in accordance with Chapter 16 of NFPA 30 (depending on the storage array inside the room). Generally, rooms with containers more than 5 gallons will require sprinkler system densities of 0.25/3,000 gpm/ft2 or greater (depending on variables such as storage array, height and sprinkler temperature).
- Room heat provided by indirect means or by equipment listed for such applications.
Detached Buildings & Hazardous Materials Lockers
In Chapters 13 and 14 of NFPA 30, there are two other options related to the liquid storage room. There is no limit to the total quantity of liquids stored in a liquid warehouse, however, the storage heights and maximum quantity per pile or rack section for unprotected storage must be in accordance with the following table: