Report Number: FP-70-12
Release Date: March 19, 2004
Section Title: Occupancy Hazards
Flammable and combustible liquids storage presents a serious fire protection challenge. The presence of these liquids in storage areas significantly adds to the fire load of a property. During a fire, flammable liquids containers may fail and spill their contents, creating more fuel for the fire. This report provides loss control considerations for the incidental storage of flammable and combustible liquids, in containers, in general purpose warehouses, mercantile, office and institutional occupancies.
Flammable and combustible liquid containers can be found in storage in any occupancy. Storage locations should be designed and configured to protect the containers form hostile fire and to contain any fires that may occur in the area. While containers for the storage of flammable and combustible liquids may be constructed of glass, plastic, and metal; plastic containers are most often used to package flammable liquids, such as kerosene, motor oil, paints, paint thinner, and rubbing alcohol.
This report provides considerations for the incidental storage of flammable and combustible liquids in occupancies not specifically designed as inside liquid storage areas, such as warehouses, mercantile, office and institutional occupancies. This report does not include considerations for the storage of flammable and combustible liquids stored in portable tanks, intermediate bulk containers, outside locations, or inside liquid storage areas, such as cutoff rooms or liquids warehouse.
NFPA 30, Flammable and Combustible Liquids Code, published by the National Fire Protection Association (NFPA), includes a system for categorizing liquids as being flammable or combustible. These liquid classifications are used for determining the various requirements within this code and other NFPA Codes. The system is based primarily on the flash point of the liquid; that is, the minimum temperature at which sufficient vapor is given off the liquid to form an ignitable mixture with air.
Flammable liquids (Class IA, IB, IC) are liquids that have flash points below 100 ºF (37.8 ºC) or less and a vapor pressure not exceeding 40 psia (2068.6 mm Hg) at 100 ºF (37.8 ºC); combustible liquids (Class II, IIIA, and IIIB) are liquids that have flashpoints of 100 ºF (37.8 ºC) or more. Class I liquids are the most hazardous from a fire safety standpoint, while Class IIIB liquids are the least hazardous of the classes. This handout describes these NFPA
- Class IA liquids – those liquids that have flash points below 73 °F (22.8 °C) and boiling points below 100 °F (37.8 °C). Additionally, unstable flammable liquids are treated as Class IA liquids.
- Class IB liquids – those liquids that have flash points below 73 °F (22.8 °C) and boiling points at or above 100 °F (37.8 °C).
- Class IC liquids – those liquids that have flash points at or above 73 °F (22.8 °C), but below 100 °F (37.8 °C).
- Class II liquids – any liquid that has a flash point at or above 100 °F (37.8 °C) and below 140 °F (60 °C).
- Class IIIA liquids – any liquid that has a flash point at or above 140 °F (60 °C), but below 200 °F (93 °C)
- Class IIIB liquids – any liquid that has a flash point at or above 200 °F (93 °C).
It is important to be aware that the NFPA classification system is based upon flash points that have been corrected to sea level. At high altitudes, the actual flash point of the liquid will be lower due to the reduced atmospheric pressure. This will affect the degree of fire risk when handling such liquids.
The storage requirements of flammable and combustible liquids in containers will vary dependent on the type of occupancy, the liquids classification, and the container size and construction. Containers for flammable and combustible liquids should be specifically listed, by an independent third party, as suitable for the material to be stored. In no case should storage obstruct an exit or exit path or create a greater hazard to the occupants of the premises. Regardless of the occupancy, Class I liquids should not be stored in basements. Additional requirements based on the occupancy type include:
NFPA 30 permits limited quantities of flammable and combustible liquid products to be stored in General-Purpose Warehouses (GPW’s) when the warehouse is separated form other occupancies by fire wall having a minimum fire resistance rating of 4-hours. GPW’s should be protected by an automatic sprinkler system, designed and installed according to the provisions of according to the provisions of NFPA 13, Standard for the Installation of Sprinkler Systems, published by the National Fire Protection Association (NFPA), for 20-ft (6-m) high storage of Class IV commodities. Container size is limited as follows:
- Class IB and IC liquids in containers of 1.3 gal (5 L) or less capacity
- Class II liquids in containers of 5.3 gal (20 L) or less capacity
- Class III liquids in containers of 60 gal (230 L) or less capacity.
In addition, the total quantity and storage-height of the liquids are limited to the following:
- Class IB and IC liquids: maximum 660 gal (2,498 L) and 5 ft (1.5 m) high.
- Class II liquid: maximum 1,375 gal (5,204 L) and 5 ft (1.5 m) high.
- Class IIIA liquid: maximum 2,750 gal (10,409 L) and 10 ft (3.0 m) high.
- Class IIIB liquid: maximum 13,750 gal (52,044 L) and 15 ft (4.6 m) high.
Any storage exceeding these limitations should be either in a dedicated inside flammable liquids room meeting the design requirements of sub-section 6.4 or in a detached liquids warehouse. Limited quantities of combustible commodities also can be stored in a GPW provided that the commodities are separated from the liquids by a minimum distance of 8 ft (2.4 m) horizontally, either by aisles or by open racks, and protected by an automatic sprinkler systems as previously described.
Storage in Plastic Containers
NFPA 30 does not permit the storage of Class I and Class II liquids in plastic containers in GPWs, unless such storage is restricted to an inside liquid storage area. However, NFPA 30 subsection 18.104.22.168 does allow Class I and Class II liquids in GPW’s when the products are packaged in individual containers: having not more than 50-percent water-miscible liquids, with the remaining solution not being a Class I liquid; not exceeding 16 oz (0.5 L) and having more than 50-percent water-miscible liquids; or the packaging systems is listed and labeled for these liquids.
A water miscible liquid mixes in all proportions with water. When water miscible flammable liquids are mixed with water, a homogeneous solution is formed. The flash point, fire point, heat of combustion, and the heat release rate of the solution will be different from the pure flammable liquid. The flash point and fire point of the solution will increase as the water concentration increases. At a certain water concentration, which varies for different flammable liquids, the fire point will no longer exist and the solution will no longer present a fire hazard. Liquids that are water-miscible include low molecular weight (3 carbons or less) alcohols, such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, and allyl alcohol, as well as acetone and tetryl-butyl alcohol.
Dispensing of Liquids
Class I and Class II liquids should not be dispensed in GPW’s unless the operations are performed in a room or area cutoff form all other areas and designed for such operations. Class I and Class II liquids should not be transferred between containers unless both containers are bonded and grounded. Proper bonding/grounding is required to prevent the buildup of static electricity produced by the transfer of liquids. Provisions for bonding and grounding include: connecting the containers to each other electrically, before transferring the liquid; and connecting both containers electrically to earth ground, before transferring the liquid.
See Fire Protection Report FP-70-08, Static Electricity, for additional information on this topic.
The storage and display of flammable and combustible liquid storage in mercantile occupancies should be carefully reviewed to ensure that the arrangement and quantities are in accordance with NFPA 30, subsection 6.5.6. Specific storage requirements will vary based on the level of fire protection provided including:
- The maximum quantity of Class I and Class II liquids that may be stored above the ground floor is limited to 120 gal (454 L) for areas protected by an automatic sprinkler system. This quantity should be reduced to 60 gal (230L) when not protected by an automatic sprinkler system.
- Class I and Class II liquids may not be stored below grade.
- Containers displayed and accessible to the public should be limited to 5.3 gal (20 L), except distilled spirits packaged in wooden barrels or cask.
- Non-water miscible Class II liquids in plastic containers having a capacity of 1 gal (3.8 L) or more shall be limited to a total of 30-gal (114-L) per storage pile and maintain at least 50-ft (15-m) separation between storage arrangements. This quantity may be doubled if the liquid is stores in a listed flammables cabinet or are protected by an automatic sprinkler system having a design density of 0.60 gpm/ft2 (24.4 mm/min).
Mercantile occupancies storage of flammable and combustible liquids is also limited by the type for fire protection system present. These limitations are detailed in table 22.214.171.124 including:
- Unprotected storage is limited to no more than 60 gal (230 L) of Class 1A liquids; 3,750 gal (14,195 L), in any combination, of Class IB, IC, II and IIA liquids per location. No more than two locations are allowed per building and they must be separated by a two-hour fire rated wall;and 15,000 gal (56,781 L) of Class IIIB liquids.
- Storage protected by a automatic sprinkler system meeting the design requirements of NFPA 13 for a Ordinary Hazard Group 2, is limited to no more than 120 gal (454 L) of Class 1A liquids; 7,500 gal (28,390 L), in any combination, of Class IB, IC, II and IIA liquids per location. No more than two locations are allowed per building and they must be separated by a two-hour fire rated wall; and an unlimited amount of Class IIIB liquids.
- Storage quantities of greater than 7,500 gal (28,390 L), in any combination, of Class IB, IC, II and IIA liquids must be protected by fire suppression systems in accordance with section 6.8 of NFPA 30.
- Table 126.96.36.199 also provided maximum storage densities (i.e. gal/ft 2 (L/m2)) for Class IB, IC, II and IIA liquids.
Offices and Institutional Occupancies
Storage of flammable and combustible liquids in offices, educational, institutional, and daycare occupancies should be limited to those materials and quantities necessary to support daily operations. Class I liquids containers located outside of a designated liquid storage areas, should be limited to a 1.3-gal (5-L) capacity, 2.6 gal (10 L) for listed safety cans). The maximum combined volume of Class I and Class II liquids stored outside of a flammables cabinet or inside liquid storage areas should not exceed 10 gal (38 L) or 25 gal (95 L) if stored in listed safety cans. Storage of Class IIIA liquids stored outside of a flammables cabinet or inside liquid storage areas should not exceed 60 gal (230 L).
Storage in excess of 25 gal (95 L) of Class I and Class II liquids combined or 60 gal (230 L) of Class IIIA, is prohibited in residential buildings, of three or less dwellings units including garage areas. Assembly occupancies and residential buildings having four or more dwelling units are limited to a maximum storage, outside of flammable cabinets or inside liquid storage areas, of 10 gal (38 L) of Class I and Class II liquids combined or 60 gal (230 L) of Class IIIA liquids.
A basic fire prevention goal in the storage of flammable and combustible liquids is to eliminate sources of ignition in areas where materials are stored, reduce the amount of easily ignitable material present near sources of ignition, and prevent contact of an ignition source with any flammable vapor/air mixture.
Building services should meet local fire and building code requirements. The electrical system should comply with NFPA 70, National Electric Code. Equipment subject to static accumulation, such as racks, ventilating ducts, hoists, etc., should be grounded. Electrical equipment of the “explosion proof” type, as defined by NFPA 70, should be used in storage areas. Gas service should comply with NFPA 54, National Fuel Gas Code. Heating/air conditioning systems should comply with the requirements of NFPA 90A, Standard for the Installation of Air Conditioning and Ventilating Systems. Heating systems for flammable liquid storage areas should be of the type that does not introduce an ignition source, such as steam or hot water.
Smoking should not be permitted in areas where flammable liquids are stored. If employee smoking is permitted in the facility, designated areas are desirable as well as the provision of noncombustible ash trays or receptacles. “No Smoking” signs should be posted in all areas where smoking is not permitted.
Measures should be taken to reduce the risk of fire from the use of powered industrial trucks in flammable liquid storage areas. The types of powered industrial trucks used should be suitable for the commodities stored, as required by NFPA 505, Fire Safety Standard for Powered Industrial Trucks Including Type Designations, Areas of Use, Conversions, Maintenance, and Operation. The standard applies to forklift trucks, tractors, platform lift trucks, motorized hand trucks, and other specialized industrial trucks, powered by electric motors or internal combustion engines, and provides information on their safe use, maintenance, and operation to minimize fire hazards.
Hot-work operations, such as welding and cutting, in flammable liquid storage areas should comply with NFPA 51B, Standard for Fire Prevention During Welding, Cutting, and Other Hot Work. A hot-work permit should be issued and a person appointed with responsibility for implementing a fire prevention program. A fire watch should be maintained during hot-work operations, and for not less than 30-minutes following completion of the operation. See Fire Protection Report FP-99-18, Hot Work Permit for additional information on this topic.
Lightning protection should be considered for outside storage areas in regions highly susceptible to lightning-strikes. Lightning protection should be installed in accordance with NFPA 780, Standard for the Installation of Lightning Protection Systems.
References Engineering and Safety Service. Control of Static Electricity. Fire Protection Report FP-70-08. Jersey City, NJ: ISO Services, Inc., 2002.
- Storage of Flammable and Combustible Liquids in General Purpose Warehouses. Fire Protection Report FP-99-29. Jersey City, NJ: ISO Services, Inc., 2004.
- Hot Work Permit. Fire Protection Report FP-99-18. Jersey City, NJ: ISO Services, Inc., 2003.
- Factory Mutual Engineering Corp. General Storage Safeguards. Property Loss Prevention Data Sheet 8-0. Norwood, MA:FM Global, 2000.
- National Fire Protection Association (NFPA), Fire Protection Handbook. 19th ed. Quincy, MA: NFPA, 2003.
- Flammable and Combustible Liquids Code. NFPA 30. Quincy, MA: NFPA, 2003.
- National Electrical Code. NFPA 70. Quincy, MA: NFPA, 2002.
- Recommended Practice for Electrical Equipment Maintenance. NFPA 70B. Quincy, MA: NFPA, 2002.
- Standard for the Fire Protection of Storage. NFPA 230. Quincy, MA: NFPA, 2003.
- Standard for the Installation of Sprinkler Systems. NFPA 13. Quincy, MA: NFPA, 2002.
- Standard for the Installation of Warm Air Heating and Air-Conditioning Systems. NFPA 90B. Quincy, MA: NFPA, 2002.
COPYRIGHT ©2004, ISO Services Properties, Inc.
The information contained in this publication was obtained from sources believed to be reliable. ISO Services Properties, Inc., its companies and employees make no guarantee of results and assume no liability in connection with either the information herein contained or the safety suggestions herein made. Moreover, it cannot be assumed that every acceptable safety procedure is contained herein or that abnormal or unusual circumstances may not warrant or require further or additional procedure.