Flammable Liquid Storage
Properties, Classification, Quantities, Cabinets, Containers and Refrigerators
The Occupational Safety and Health Administration (OSHA), the National Fire Protection Association (NFPA), and the California Fire Code (CFC) define flammable liquids as any liquid that has a flash point of less than 100oF (38oC)1 and combustible liquids as those that have a flash point greater than 100oF (38oC). These are further categorized into the following subdivisions based on the flashpoint and/or boiling point.
Class IA. Liquids having a flash point below 73oF (23oC) and having a boiling point below 100oF (38oC).
Class IB. Liquids having a flash point below 73oF (23oC) and having a boiling point above 100oF (38oC).
Class IC. Liquids having a flash point at or above 73oF (23oC) and below 100oF (38oC).
Class II. Liquids having a closed cup flash point at or above 100oF (38oC) and below 140oF (60oC).
Class IIIA. Liquids having a closed cup flash point at or above 140oF (60oC) and below 200oF (93oC).
Class IIIB. Liquids having a closed cup flash point at or above 200oF (93oC).
Classification of Flammable and Combustible Liquids
The properties of flammable materials are of critical importance in the safe storage and use of these materials. The flash point of a liquid is defined as the minimum temperature at which a liquid gives off sufficient vapor to ignite in the presence of a source of ignition. Remember, it is the vapor that burns and not the liquid.
- The Department of Transportation (DOT) and American National Standards Institute (ANSI) define flammable liquids as those with a flash point less than 140OF which includes NFPA Class II combustible liquids.
The following table provides the flashpoint, boiling point, and NFPA classifications of some common laboratory chemicals:
Mixtures of soluble flammable chemicals and water also affect the flammable properties of these solutions. The following table summarizes the various properties of ethyl alcohol and water solutions.
Maximum Allowable Quantities
The maximum allowable quantities of flammable or combustible liquids allowed in a control area (laboratory or suite of laboratories) are limited by the location in the building and the construction specifications. Typical laboratories are not constructed to high hazard group specifications (check with the facility manager).
The following table shows the maximum allowable quantities that can be stored in a single fire control area (laboratory or suite of laboratories) per floor. Note that quantities may be increased when using approved flammable cabinets and in areas equipped with fire suppression sprinklers. The maximum allowable quantity is the total aggregate quantity of liquids stored inside cabinets, outside cabinets, and in safety cans.
- Maximum quantities shall be increased 100% for buildings equipped throughout with an automatic sprinkler system. Where note b applies, the increase for both shall be applied accumulatively.
- Quantities shall be increased 100% when stored in approved cabinets, gas cabinets, exhausted enclosures, or safety cans as specified by the International Fire Code. Where noted applies, the increase for both shall be applied accumulatively.
- The permitted quantities shall not be limited in buildings equipped throughout with an automatic sprinkler system and provided with exhaust ventilation.
- Containing not more than the maximum allowable quantity per control area of Class 1A, 1B, or 1C flammable liquids.
Quantity Limits Outside Flammable Storage Cabinets
No more than ten (10) gallons of flammable or combustible liquids may be stored outside a flammable cabinet (with the exception of materials stored in approved safety cans).
Quantity Limits Inside Flammable Storage Cabinets
Flammable liquids stored inside flammable storage cabinets are limited to 60 gallons of Class 1A flammable liquids per cabinet. The total volume of combined classes of flammable and combustible liquids may not exceed 120 gallons per cabinet.
Flammable Cabinets must meet the construction specifications of NFPA 30, Flammable and Combustible Liquids Code, and the California Fire Code. Cabinets must be Underwriter Laboratories (U.L.) 1275 listed which is indicated by a permanent label on the cabinet affixed by the manufacturers. Self-closing doors with a three point latch are required per the California Fire Code, Section 3404.3.2.1.3. Cabinets should be placed so that they do not block or impede egress.
NFPA 30 does not require flammable cabinets to be ventilated. If not vented, the vent openings must be sealed. If vented, the vent openings must be equipped with spark arrestors. The supply and exhaust must be ducted to the outside and the flow must be installed with supply provided at the top and exhaust exiting at the bottom of the cabinet. UC Davis Fire Prevention must approve venting of any flammable storage cabinet (see UC Davis FireNet, “Venting Flammable Storage Cabinets”).
Grounding is not required unless Class IA flammable liquids are being dispensed from the cabinet. If grounding is desired, the cabinets must be grounded to a static grounding terminal and not to the ground of an electrical receptacle.
The California Code of Regulations Title 8, Section 5532 and OSHA 1910.106 define the maximum allowable capacity for containers used in laboratories.
Individual glass containers of Class IA liquids must not exceed 1 pint (500 ml) capacity. Individual glass containers of Class 1B liquids must not exceed 1 quart (1 liter) capacity. Exception: Class I-A and I-B liquids may be stored in factory-shipped glass containers up to 1- gallon or 4-liter capacity if the required liquid purity would be affected by storage in metal containers or if the liquid would cause excessive corrosion of a metal container.
Class I-A liquids can be stored in metal containers not larger than 1 gallon (4 liters) capacity, orU.L. listed safety cans not larger than 2 gallons (8 liters) capacity.
For liquids other than Class I-A liquids, the capacity of the containers regardless of type (i.e., metal, glass, etc.) must not exceed five (5) gallons each.
Improper storage of flammable liquids in household-type domestic refrigerators can be very dangerous and present the risk of personal injury and/or property damage. The accumulation of vapors in this confined space can result in an explosion or fire if these vapors are ignited by the various electrical components inside the refrigerator compartment. These sources of ignition include temperature controls, thermostats, relays, light switches, light assemblies, defrost mechanisms, fans, and even mechanical door latches.
There are four types of refrigerators found in laboratories:
- Domestic refrigerator/freezers used for storage of non-flammable chemicals only.
- Modified domestic refrigerators that have all the electrical components re-located outside the inner compartment to make them suitable for the storage of flammable liquids.
- Laboratory-safe or flammable material refrigerator/freezers used for the storage of flammable chemicals in laboratories.
- Explosion proof refrigerator/freezers used for the storage of flammable chemicals in hazardous locations.
Storage of chemicals in refrigerated environments requires proper precautions:
- Keep all containers tightly closed.
- No open containers (no open beakers, test tubes, flasks, bottles, or other containers).
- Make sure that the integrity of the container and the lid or stopper is adequate.
Domestic household refrigerators have internal components located inside the inner compartment such as thermostats, lights, and switches that can create a spark capable of igniting vapors from flammable liquids stored inside.
This type of refrigerator is the lowest cost so many labs use this type of refrigerator for storing non-flammable chemicals. Domestic Refrigerators must be labeled properly. Flammable materials must never be stored in this type of refrigerator.
Modified Domestic Refrigerator/Freezers
Some laboratories have existing modified domestic household refrigerators that have had the internal components re-located outside the inner compartment by qualified electricians to make them safe for storage of flammable materials. The National Fire Protection Association (NFPA 45) Standard on Fire Protection for Laboratories Using Chemicals, describes the modification procedure and the proper notices to be used. This practice is not recommended.
Extreme caution should be exercised because in some cases not all the possible sources of ignition may have been isolated. Using previously modified refrigerators is acceptable if the laboratory inspects them regularly for defects such as frayed wiring. Defective refrigerators should not be used to store flammable materials.
Notice: This is not an explosion proof refrigerator, but it has been designed to permit the safe storage of materials producing flammable vapors. Containers should be well- stoppered or tightly closed.
Laboratory-Safe or Flammable Material Refrigerator/Freezers
Laboratory-safe refrigerators are designed to prevent ignition of flammable vapors or gases that may be present inside the refrigerator only. Laboratory-safe or flammable material refrigerator/freezers should be purchased whenever a refrigerator is needed to store flammable liquid.
These refrigerator/freezers are designed to prevent ignition of flammable vapors inside the storage compartment. All the electrical components in this type of refrigerator are located outside the refrigerator, and the compressor is sealed or located at the top of the unit. Flammable material refrigerators also may incorporate design features such as thresholds, self-closing doors, magnetic door gaskets, and special inner shell materials that control or limit the damage should a reaction occur within the storage compartment. The refrigerators must be U.L. Listed as Flammable Material Storage Refrigerators. Ultra low freezers (less than -40°F) generally cannot be approved for storage of flammable materials.
Explosion Proof Refrigerator/Freezers
Explosion-proof refrigerators are designed to prevent ignition of flammable vapors or gases that may be present inside and outside the refrigerator. This type of refrigerator is used in locations such as solvent dispensing rooms, where a flammable atmosphere may develop at some time in the room. Explosion-proof refrigerators have very limited use and require special hazardous-location wiring rather than the simple plug-in type power cord. Consult with the UC Davis Fire Prevention Office before purchasing an Explosion Proof Refrigerator.