Refrigerators and Freezers
This common piece of lab equipment is generally used for storage of reactive chemicals or biological specimens. Refrigerators and freezers can create hazardous situations if the incorrect type of unit is employed or if there is a loss of power.
The potential hazards posed by laboratory refrigerators and freezers involve concentration of vapors, the possible presence of incompatible chemicals, and spillage. Loss of electrical power can produce extremely hazardous situations due to the concentration of vapors. Flammable or toxic vapors may be released from containers as chemicals warm up and/or certain reactive materials may decompose energetically upon warming. These concentrated vapors may leak out of the unit after concentrating within. This may pose a fire/explosion hazard or a toxicity hazard depending on the nature of the chemicals stored within.
Flammable Liquid Storage Units
Standard "domestic" refrigerators contain lights, switches, and thermostats in the refrigerated area. These features are potential ignition sources for flammable vapors. Therefore, flammable chemicals or chemical mixtures that must be kept below room temperature must be stored in refrigerators or freezers specifically designed by the manufacturer for storage of flammable liquids. Flammable liquid-approved refrigerators are designed with spark-producing parts on the outside to avoid accidental ignition.
A flammable liquid rated unit is very likely the best for your lab chemical storage needs. If flammable chemicals are never to be stored in the unit, then a domestic unit may be used for biological samples.
All materials with a flashpoint below 100° F may only be stored in an approved flammable materials storage refrigerator or freezer.
Refrigerators and freezers that do not have ignition sources inside or outside of the unit are called explosion-proof units. These units are designed for cold storage of flammable liquids in a room that has a potentially explosive atmosphere.
Here is the difference between the two types:
- Flammable storage refrigerators and freezers have no exposed ignition sources inside the cabinet, such as lights or switches, which could ignite vapors.
- Explosion-proof or spark-proof units have no interior or exterior ignition sources. An explosion-proof refrigerator or freezer may be required in rare circumstances in hazardous locations.
Refrigerators and freezers should be labeled clearly for their intended purpose (e.g., “No Food or Drink to be Stored in this Refrigerator”, “Refrigerator For Food Only”, "NO FOOD - CHEMICAL STORAGE ONLY", "Not For Flammable Storage", etc.). It is possible that a unit may require multiple labels. All ordinary domestic refrigerators and freezers should be labeled with the phrase “No materials with a flashpoint below 100° F may be stored in this refrigerator/freezer” or “Not for flammable storage.
All materials in refrigerators or freezers should be labeled with the contents, owner, date of acquisition or preparation, and nature of any potential hazard. All containers should be sealed, preferably with a cap, and placed in secondary containers or catch pans. Since refrigerators are often used for storage of large quantities of small vials and test tubes, a reference to a list outside of the refrigerator could be used. Labels and ink used to identify materials in the refrigerators should be water-resistant.