Laboratory Refrigerators and the Storage of Flammables
By: Lee Stone

Flammable chemicals that require refrigeration must only be stored in a refrigerator that is designed for the safe storage of flammables. A flammable liquid is defined by the fire code as having a flash point of less than 100°F (38°C). We look for improperly stored flammables during our annual Laboratory Safety Surveys and when laboratory workers are asked to remove flammables from a refrigerator that is not designed for their storage I am often asked “why?” and “what type of refrigerator should I purchase that will allow me to store my flammables safely?”. I hope this article will explain why and help you to decide the proper refrigerator for your laboratory.

The storage of flammable materials in household-type refrigerators or a laboratory refrigerator that is not designed for flammable storage is a risky practice due to the potential of vaporization of these materials in the closed space and explosion of those vapors from a spark generated by electrical contacts from relays, switches, or thermostats that could ignite flammable vapors inside the refrigerator. While this has not happened on our campus, there are many reported incidents at other institutions that have caused injuries and property damage from this type of explosion.

There are 3 types of refrigerators that can be found in the laboratory:

1. Ordinary Household Refrigerator

Household refrigerators like the one seen in figure 1 have internal components such as thermostats, relays and switches that can create a spark that is capable of igniting vapors generated from flammable liquids stored inside of them. This type of refrigerator is the lowest cost and because of the lower cost many labs have only this type of refrigerator. Flammable materials must never be stored in this type of refrigerator.

Figure1: Household Refrigerator

2. Flammable Storage Refrigerator

	Flammable storage refrigerators like the one seen in figure 2 are UL approved for storage of flammable chemicals. Flammable storage refrigerators have no electrical sparking devices, relays, switches, or thermostats that could ignite flammable vapors inside the cabinet. Flammable storage 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. A label stating “Flammable Materials Refrigerator: Keep fire away” can identify such refrigerators.
Figure 2: Flammable Storage Refrigerator	The refrigerators must be U.L. Listed as Flammable Material Storage Refrigerators.
Flammable storage units cannot be placed in a room containing explosive vapors but chemicals that exude explosive vapors can be safely stored inside them. These refrigerators are also called lab-safe, fire-safe and/or explosion safe refrigerators. These refrigerators are more costly than the household refrigerator types but they must be purchased if you are planning on storing flammables in the refrigerator.

3. Explosion Proof Refrigerator

	Explosion proof refrigerators like the one seen in figure 3 are rated UL explosion-proof and are similar in design to the flammable storage units, but also have all operating components sealed against entrance of explosive vapors. Electrical junction boxes are also sealed after connections are made. These units are approved for storage of volatile materials in areas with explosive atmospheres and are the most costly of all types. This type of refrigerator is only required when storing flammable materials in an area with an explosive atmosphere such as a solvent dispensing room.
Figure 3: Explosion Proof Refrigerator	Explosion-proof refrigerators have very limited use on campus and require special hazardous-
location wiring rather than simple cord-and-plug connections. Please contact Lee Stone, IUPUI Laboratory Safety Manager, at 278-6150 if you feel you have a need for an explosion proof refrigerator. Since TEMED or Sigmacote are the only flammable materials stored in the refrigerator for many labs, Sigma was contacted concerning storage options for these chemicals. Sigma Corporation representative Dr. Jeffrey Howard responded that storage of both of these materials in the refrigerator is optimal but it is not necessary. Both of these chemicals may be stored in a solvent cabinet as long as the lab is maintained at room temperature without extreme fluctuations. Dr. Howard states that both chemicals are stable at room temperature for several months. Due to the moderately low cost of both of these chemicals, it is recommended that they be stored at room temperature if there is no flammable storage refrigerator available. Date the chemical when received and dispose after several months to insure effective results with its use. Please look in your refrigerator now and remove any flammable materials if it is not approved for the storage of flammables.