Storage of Laboratory Chemicals

The following general suggestions for safe storage of chemicals in the laboratory should be implemented.

• The quantities of chemicals that are stored within a laboratory should be minimized, as specified by NFPA 45 and OSHA. 
• Bulk quantities of chemicals (i.e., larger than one gallon) must be stored in a separate storage area. Transfer of flammable liquid from five gallon or larger metal containers may not be done in the laboratory.
• Chemicals should be stored in accordance with the manufacturer's recommended temperature and humidity level. Chemicals should not be stored near heat sources, such as steam pipes or laboratory ovens. Chemicals should never be stored in direct sunlight.
• Chemicals should be dated when received and when opened. Time-sensitive chemicals should also include an expiration date.
• Visual inspection of the material and its container should be conducted routinely. Indications for disposal include:
  • Cloudiness in liquids
  • Material changing color
  • Evidence of liquids in solids or solids in liquids
  • “Puddling” of material around outside of container or pressure build-up within bottle
  • Obvious deterioration of container
• Chemicals should not be routinely stored on the benchtops. In such locations they are unprotected from exposure and participation in a fire situation and are also more readily knocked over. Each chemical should have a specific storage area and be returned there after use.
• Large quantities of flammable materials should not be stored in the laboratory. Only the amounts needed should be kept on benchtops, the remainder should be kept in flammable storage cabinets.
• Laboratory shelves should have a raised lip along the outer edge to prevent containers from falling.  Never allow chemical containers to extend over the edge of the shelf.  Liquid or corrosive chemicals should never be stored on shelves above eye-level. Glass containers should not touch each other on the shelves.
• Secondary containers or trays should be used for chemical storage whenever possible to minimize the flow of material should a spill or rupture occur. Round bottom flasks should always be supported properly in cork rings or by other means to keep them from tipping.
• Adequate security must be provided so that unauthorized personnel do not have access to hazardous materials.
• Chemicals may not be stored on the floor for any amount of time.
• Chemicals no longer needed for research purposes may be offered to other labs on the same campus or must be disposed of in accordance with campus regulations.
• Flammable materials must never be stored in domestic-type refrigerators. Only explosion-proof or flammable material refrigerators should be used for storage of these chemicals within a laboratory environment.
• Refrigerated chemicals must be tightly capped to reduce vapors and alleviate odors. Flasks stoppered with cork, rubber, or glass should be wrapped with Parafilm to reduce leakage.
• Inventory the materials in refrigerators frequently to avoid overcrowding with materials that have long since been forgotten. Also make it a point to defrost refrigerators occasionally so that chemicals do not become trapped in unique ice formations!
• Before storing materials in a refrigerator, ensure that refrigeration is necessary. Never store peroxide formers in a refrigerator.
• Fume hoods should not be used as general storage areas for chemicals. This may seriously impair the ventilating capacity of the hood.
• Gas cylinders must be securely strapped to a permanent structure (wall, lab bench, etc.). When they are not in use they should be capped.

Segregation Based on Hazard Classes

Incompatible materials must be segregated according to hazard class. Hazards are indicated both on the chemical container label and the Safety Data Sheet (SDS) accompanying the chemical. Chemicals must be segregated, at a minimum, into the following major categories:

• Flammables
• Oxidizers
• Acids
• Bases
• Corrosives
• Highly Reactives
• Acutely Toxics/Regulated Materials
• Low Hazard

Other considerations for chemical segregation include:

• Many chemicals present multiple hazards and must thus be further segregated within the major hazard classes listed above.
  
  • Segregation should start with flammability - all flammable liquids should be stored in a flammable cabinet or an approved flammable storage refrigerator. Flammable solids should be stored in a cool dry location away from any potential sources of ignition.
  • Oxidizers and explosives should be segregated, especially from flammables, as they may contribute significantly to a fire.
  • Water reactive material must be stored in a manner that prevents exposure to water and/or high humidity. Air reactives must be stored under inert gas or in another approved manner that prevents exposure to the atmosphere.
  • Corrosive materials should be segregated into acids and bases. Acids should be further segregated as either organic or inorganic.
  • Some materials, such as controlled substances and acutely toxic chemicals, may require secure locked storage within a designated storage area. Segregate by hazard class, then restrict access.

Peroxide-Forming Materials

Peroxide-forming materials are chemicals that react with air, moisture, or impurities to form organic peroxides. Organic peroxides are also formed in these materials during evaporation or distillation.

Peroxides formed by materials in the lab can be extremely sensitive to shock, sparks, heat, friction, impact, and light. Exposure to these elements can result in a violent explosion. The friction from unscrewing the cap of a container of a peroxide-containing chemical can provide enough energy to cause a severe explosion.

Use and Storage of Peroxide-Formers

• Visually inspect liquid peroxide-forming materials for crystals or unusual viscosity before opening, paying special attention to the area around the cap. Peroxides can form upon evaporation and may crystallize on the threads under the cap. Do not open the chemical container if peroxide formation is suspected.
• Date all peroxide forming materials with the date received, and the expected shelf life. Chemicals such as diisopropyl ether, divinyl acetylene, sodium amide, and vinylidene chloride should be discarded after three months. Chemicals such as dioxane, diethyl ether, and tetrahydrofuran should be submitted to Environmental Management (division of IUEHS) for proper disposal after one year.
• Store all peroxide-forming materials away from heat, sunlight, and sources of ignition. Sunlight accelerates the formation of peroxides.
• Secure the lids and caps on these containers to discourage the evaporation and concentration of these chemicals.
• Never store peroxide-forming materials in glass containers with screw cap lids or glass stoppers. Friction and grinding must be avoided. Also, never store these chemicals in a clear glass bottle where they would be exposed to light.
• If crystal formation is observed within the container or around the lid, do not move or attempt to open the bottle. Call IUEHS for proper disposal.
• Never distill an ether unless it is known to be free of peroxides.