By: K. Lee Stone


Lee Stone has a Master's degree in toxicology from Indiana University and is a certified Chemical Hygiene Officer. Lee has served as the Laboratory Safety Manager for the Office of Environmental Health and Safety since 2004.


E-mail Lee Stone at: leestone@iupui.edu



Exploding Refrigerators in the News

There was a recent explosion in a University of South Florida Laboratory that made the news. The explosion occurred inside of a refrigerator with such force that the door of a full-sized refrigerator had been blown off and traveled 20 feet through the air across the entire laboratory where it shattered a window. I have not heard what the cause of this explosion was but there is a good chance it was the result of flammable chemicals improperly stored in a household refrigerator.


The storage of flammable materials in a household-type refrigerator, or a laboratory refrigerator that is not designed for flammable storage, is risky practice. This is due to the potential of vaporization of these materials in the closed space and potential explosion. Explosion of flammable vapor 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.


Below are photos and descriptions of the 3 types of refrigerators that can be found in the laboratory.


1. Ordinary Household Refrigerator.


Household refrigerators like the one shown below have internal components such as thermostats, relays and switches. All these components have the capability of generating a spark. If a spark is generated it is capable of igniting accumulated vapor released from flammable liquids stored inside the refrigerator. This type of refrigerator is the least costly 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.



2. Flammable Storage Refrigerator


Flammable storage refrigerators, like the one seen below 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. 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 below 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 refrigerator 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. 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 of it after several months to insure effective results with its use.


Please help keep our campus safe. Identify the type of refrigerators you have and remove any flammable materials if your refrigerator is the type not approved for the storage of flammables.



Lab Notes is a quarterly publication by the IUPUI Office of Environmental Health and Safety. Lab Notes is designed, edited and published by K. Lee Stone.

"Don't Learn Laboratory Safety by Accident!"