Laboratory Refrigerators are used to store volatile, noxious and air sensitive materials and it is not uncommon for the atmosphere inside the unit to be saturated with chemical vapors. Over time, these vapors can penetrate porous surfaces and lead to odor problems. Similarly, material from spills or leaking containers can impregnate surfaces that then give off odors long after the original material is cleaned up.
In addition to problems associated with odor, accumulated vapors arising from chemicals stored in laboratory Refrigerators present a flammable or explosive hazard due to the in-built ignition sources in the refrigerators. Loss of electrical power can produce extremely hazardous situations. Flammable or toxic vapors may be released from refrigerators and freezers as chemicals warm up and/or certain reactive materials may decompose energetically upon warming.
Examples of ignition sources within household refrigerators include:
• Switches associated with the internal light and thermostat;
• Timers and heating elements in frost free refrigerators;
• The compressor motor, if the cabinet is not effectively sealed and vented from water in
the drain tube of frost free refrigerators or chemicals present in the refrigerator;
Types of Refrigerators/Freezers
There are primarily three different types of refrigerators/freezers for chemicals:
1.Household (Domestic): Although not recommended for laboratory use, household refrigerators and freezers may be used for storage of aqueous solutions. Liquid and solid chemicals should not be stored in these refirgerators.
2.Lab-Safe (or Explosion-Safe or Flammable): Refrigerators and freezers are used for storage of flammable or explosive materials. This type of cooling technology has no internal switching devices that can arc or spark as a source of ignition. The compressor and other circuits usually are located at the top of the unit to reduce the potential for ignition of flammable vapors. These refrigerators also incorporate features such as thresholds, self-closing doors, and magnetic door gaskets. Special inner shell materials limit damage should an exothermic reaction occur within the storage compartment.
3.Explosion-Proof: Laboratory refrigerators are designed to be operational in areas where the air outside the refrigerator might be explosive. This includes liquids, gases, or solids with flashpoints of less than 100°F. Explosion-proof refrigerators feature enclosed motors to eliminate sparking and bear a FM® (Factory Mutual) or UL®