Did you know that many explosions, injuries, and costly laboratory fires have been caused by storing flammable materials in the wrong type of lab refrigerator? As we recognize Fire Prevention Week, we wanted to shed some light on this fire-related lab hazard that can be easily overlooked.
It’s commonly known that flammables have to be stored in flammable storage cabinets, but what if they need to be kept cold for certain lab protocols? General purpose lab refrigerators (including glass deli fridges) are not designed for the storage of flammables. A flammable liquid is defined by the NFPA as a liquid having a flash point of less than 100°F (38°C).
The temperature of standard lab refrigerators (39°F or 4°C) is at, or above, the flash point of many flammable liquids. For instance, the flash point of acetone is 0°F (-18°C). This means acetone can give off enough vapor to ignite in the presence of an ignition source in a standard refrigerator. Ignition sources include the internal lights, thermostat, and defrosting mechanisms.
For that reason, flammable liquids need to be stored in flammable safe refrigerators which have electrical sparking components on the outside (usually the top) of the refrigerator. In addition, these refrigerators have other design features making them safe for flammables storage such as self-closing doors and inner shell materials that control or limit damage in the event of an explosion within the storage compartment.
Another type of refrigerator that can be used for flammable storage is an explosion-proof refrigerator. However, they are designed for areas where the air outside the refrigerator might be explosive and are not common in typical laboratory settings. They have enclosed motors to eliminate sparking and require direct wiring to a power source as opposed to a standard cord-and-plug connection. Because of the complexity of their design, they are considerably more expensive.
How do you know if you have the right type of refrigerator in your lab for cold storage of flammables? General purpose lab refrigerators often have a manufacturer label that states “Not For Flammable Materials Storage.” Flammable safe refrigerators will be identified with a “Flammables Materials Storage/Keep Fire Away” label. In addition, they must be UL (Underwriters Laboratories) listed. Explosion proof refrigerators will have an “Explosion Proof Refrigerator/Keep Fire Away” label and must also be UL listed. Note that if your laboratory refrigerator is unlabeled, it’s probably not rated for flammable storage and should not be used for that purpose!
In addition to using the right type of refrigerator for storage, don’t forget that cold rooms are not appropriate for flammable storage because they are not ventilated and have recirculated air, allowing for the buildup of flammable vapors. Cold rooms often have fans and electrical lab equipment that are potential ignition sources.
For additional information on how to safely store your flammable liquids that need to be kept cold, please contact us!
This blog was written by Beth Graham, Director of Quality, Research, and Training