Chemical Families
Materials should always be segregated and stored according to their chemical family or hazard classification. Do not store chemicals alphabetically unless they are compatible! The most common hazard classes include:
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flammables/combustibles
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corrosive acids
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corrosive bases
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toxics
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highly toxics
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oxidizers
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compressed gases
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cryogens
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pyrophorics
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water reactives
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explosives
Accidental contact between incompatible chemicals can result in a fire, an explosion, the formation of highly toxic and/or flammable substances, or other potentially harmful reactions:
Oxidizers mixed with flammable solvents can greatly increase the severity of a fire. Acids mixed with metal dust can produce flammable hydrogen gas.
Alphabetical storage can bring incompatibles together. For example, if chromic acid (an oxidizing acid) and chromium powder (a combustible metal) were stored together and an accident broke their containers, the chemicals could mix and react with explosive violence.
Segregate Families
Ideally, each hazard class would be kept in a cabinet or on a shelf segregated from other hazard classes. Incompatible chemicals within the same hazard class should also be separated from one another. For example, both nitric and perchloric acids are incompatible with organic acids (such as acetic acid) and should not be stored together.
Most labs have limited space, but the following priorities may help you decide how to store the chemicals.
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Do not store chemicals alphabetically unless they are compatible.
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Store flammable liquids in approved safety containers in flammable storage cabinets. Do not store anything but flammable or combustible liquids in these cabinets.
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Segregate acids from bases.
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Segregate most organic acids from oxidizing mineral acids.
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Keep oxidizers away from other chemicals, especially flammables, combustibles, and toxic materials.
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Keep corrosives away from substances that they may react with and release corrosive, toxic, or flammable vapors.
Multiple Hazard Classes
Many chemicals belong to more than one chemical family or hazard class. In such cases, all storage rules must be strictly observed. For example, acetic acid is both a corrosive acid and a combustible liquid. It must be stored away from corrosive bases, such as sodium hydroxide, and also from oxidizing acids, such as nitric acid.
For More Information
For more specific information, use the storage guidelines that follow. You can obtain labels and material safety data sheets (SDS) from the manufacturer, your department, or EH&S. SDS provides information on chemical compatibility.