Laboratory chemicals are stable only within prescribed temperature limits. High purity chemicals used as reference standards require preservation in low temperatures so that the concentration of active constituent does not change over their prescribed usage life. Flammable liquids also require to be stored under low temperatures so as to prevent formation of explosive vapours over storage periods.
A household refrigerator is used for preservation of foodstuffs and drinks. However, chemicals should never be stored inside a domestic refrigerator as cross- contamination by laboratory chemicals can lead to serious consequences. Laboratory refrigerators require additional built-in safety features so as to make them explosion proof. Such refrigerators should have all spark producing component parts outside the cooling chamber. Such parts include interior light switch, defrost heater, defrost control switch, compressor unit and fan.
It should be kept in mind that a refrigerator can remain in use for years together. During its long usage there are chances that someone may use it for purpose other than it is initial intended purpose. It becomes all the more important to display prominently front cover signs such as
‘Not for storage of foods, beverages or other edibles’
Recommended practices of storage of chemicals in refrigerators :
- Laboratory use refrigerators should be kept in well ventilated spaces so that there is no buildup of flammable liquid vapours in their vicinity due to presence of other flammable solvents.
- Solvent containers should be securely capped or beakers containing such solvents should be properly covered. Mere covering with aluminium foil or plastic sheet cover is not enough to prevent buildup of flammable vapours in the confined closed space over a period of time. On exceeding the lower flammability limit and due to excessive pressure buildup the door latch can fail leading to dangerous explosion on exposure to any ignition source outside.
- Chemicals stored inside the refrigerator should be compatible. Spillages if any, should be attended on top priority to prevent build-up of dangerous concentration levels. Clean spills with soap or any recommended solvent .Strong solvents can result in damage to the plastic parts of the interior compartment. Biological spills may require cleaning with 10 % bleach solution followed by cleaning with soap and water. The waste rags should be autoclaved before disposal
- Laboratory refrigerators require more frequent cleaning and defrosting than domestic refrigerators. Take adequate precautions and wear disposable gloves during cleanup operations
- Long time power failures can result in the formation of dangerous levels of flammable or toxic vapours inside the closed space. Care should be exercised when opening the door after long power failures.
Lastly it is re-emphasized that laboratory refrigerators should not be used for storage of materials other than laboratory chemicals or flammable solvents.