Chemicals should be stored according to their compatibility and hazard class. Incompatible chemicals should be segregated from each other. Consult the Safety Data Sheet (SDS) when doubts arise concerning chemical properties and associated hazards. 

The basic requirements for chemical storage and segregation are discussed in the sections below. 

• General Chemical Storage
• General Chemical Segregation
• Secondary Containment

General Chemical Storage

• Store chemicals (including gas cylinders) and chemical packages in an access restricted area.  
• Keep chemicals away from heat sources, direct sunlight, and egress pathways. 
• Assign each chemical a definite storage place and return to that place after each use. 
• Provide secondary containment for liquids whenever possible.
• Label containers, and be sure container is compatible with the chemical. 
• Keep containers closed when not in use. 
• Do Not store materials on top of high cabinets where they will be hard to reach and see.  
• Do Not store chemicals on the floor not even temporarily. 
• Do Not store chemicals in a fume hood, except for certain toxic gases which can only be stored in a gas cabinet or fume hood.  
• Do Not stack chemicals on top of each other. 
• Do Not store chemicals (except cleaners) under sinks. 
• Store flammable liquids in approved flammable liquid storage cabinets. 
• Cold rooms, refrigerators, and freezers have additional requirements, particularly for flammables. If flammable liquids need to be stored in cold temperatures, store them in flammable storage refrigerator/freezer or explosion proof refrigerator/freezer. Never store flammable liquids in household refrigerators. 
• Store highly toxic chemicals (e.g. cyanide salts) under conditions of satisfactory physical security, preferably in a locked cabinet.

General Chemical Segregation

Chemicals must be stored by compatibility, not by alphabetical arrangement. Compatibility information is available on the chemical's Safety Data Sheet (SDS). A quick and very general rule of thumb is to separate organics from inorganics, flammables from oxidizers (including gases as well as liquids), acids from bases, reactive from air or water,  and acutely toxic chemicals from other chemicals.  

Suggested chemical storage and compatibility lists can be found in a number of lab safety resources, e.g. Prudent Practices for Handling Hazardous Chemicals in Laboratories and UH Chemical Hygiene Plan (Appendix 5. Chemical Segregation and Incompatibilities Guidelines).

Secondary Containment

Secondary containment is an effective tool to enhance the safe storage and segregation of hazardous materials by the following: 

• Localize and contain spillage from defective or broken chemical containers. 
• Prevent incompatible materials from mixing. 

Ensure that secondary containment is sufficiently voluminous so that it can hold the contents of the inner containers should they break. In most cases, open-topped plastic secondary containment is satisfactory for hazardous material storage. EHS prepared “A Simple Guide for Use of Secondary Containment for Chemicals” to assist lab better utilize secondary containment for chemical storage and segregation.