Every chemical that is generally considered benign has the potential to be hazardous under specific conditions. Consult the Safety Data Sheet (SDS) when doubts arise concerning chemical properties and associated hazards.

Segregation/Storage Guidelines

  • Separate chemicals into organic and inorganic families.
  • Segregate each family according to chemical classes and compatibility (see figure below). Refer to Chemical Hazard Properties section for more information.
  • Following appropriate segregation by hazard class, remaining chemicals may be segregated and stored using a convenient finding method such as alphabetically. For detailed storage and segregation information, refer to the Chemical Hygiene Plan.
  • Ensure that all chemical bottles shall be closed when not in use.

Chemical Hazard Properties


Store flammable and combustible liquids not in use in a flammable storage cabinet or approved refrigerator or freezer. The maximum amount permitted outside a flammable cabinet, safety can or approved refrigerator or freezer is ten gallons of combined flammables, with no individual container being greater than one gallon (8CCR §5538).

  1. General Rules
    • Do not store flammable liquids on the floor or in non-approved refrigerators or freezers.
    • Label all storage areas containing flammables with the word “flammable”.
    • Flammables must be kept away from oxidizing, pyrophoric, and water reactive chemicals.
    • Do not house flammable materials in cold rooms since they are not ventilated.
  2. Flammable Cabinets
    • Must be labeled “FLAMMABLE- KEEP FIRE AWAY” in red lettering.
    • Flammable cabinets are rated for maximum capacity of 30 gallons or 60 gallons.
    • Provision of additional secondary containment for all glass bottles stored above the base is highly recommended.
    • Store materials that burn very hot and cannot be extinguished with usual extinguishants (e.g., flammable metals or self-heating chemicals) in a separate cabinet from flammable liquids.
    • If ventilation is required for your flammable cabinet, please email labsafety@usc.edu. NOTE: A tray or sock of activated carbon can be very effective at combatting buildup of vapors in flammable cabinets.
  3. Flammable Storage Refrigerator/Freezer
    • Appropriate for small amounts of flammable materials, flammable liquids (flash points < 100⁰F), and combustible liquids (flash points > 100⁰F).
    • All chemicals should be stored with consideration to incompatibilities so that if a container breaks, reactive materials do not mix and react violently.
      • Appropriately labelled secondary containment should be used to separate incompatible chemicals.
    • It is highly recommended that all glass containers in refrigerators and freezers be placed in secondary containment.
    • All refrigerators or freezers not positively identifiable as approved units shall be considered non-approved, and shall be clearly labelled “Not approved for the storage of flammables”, or words to that effect.
  4. Explosion-proof Refrigerator/Freezer
    • Appropriate for large quantities of flammables.


Next, consider reactivity. Do not store materials that may start a fire (pyrophorics, self-heating chemicals, water reactives) or contribute significantly to a fire (oxidizers, organic peroxides, explosives, self-reactive materials) with flammable or combustible materials.

  1. Oxidizing Chemicals
    • Segregate from flammable, combustible, pyrophoric, water reactive, and reducing materials.
    • Store large quantities in a dedicated noncombustible steel cabinet.
  2. Peroxide-Forming (e.g., diethyl ether, cyclohexene, dioxane, and tetrahydrofuran) and Time-Sensitive Chemicals (e.g., chloroform, formic acid, and gaseous HF)
    • Label peroxide-forming chemicals with the date received, date opened, and expiration date. Find more detailed information in the Peroxide Formers Guide Sheet.
    • Time sensitive chemicals should be purchased in inhibited form and must be disposed of by the listed expiration date. Find more detailed information on specific time sensitive chemicals in the CHP.
  3. Pyrophoric Chemicals
    • Segregate from compressed gases, flammable, combustible, oxidizing, and highly health hazardous materials.
    • Shall be stored below eye level and must be conspicuously identified.
    • Follow manufacture’s/supplier’s storage instructions to determine if inert gas-filled desiccators, gloves boxes, cold-storage, or other special storage conditions are required.
    • Label pyrophoric chemicals with the date received, date opened, and expiration date by the manufacturer/supplier.
    • NOTE: Pyrophoric materials can be incredibly hazardous if not handled or stored appropriately. Illustration of these hazards can be seen in the Learning from UCLA case study.
  4. Water-Reactive Chemicals
    • Store away from possible water sources and leaks, aqueous solutions, and acids.
    • Shall be stored below eye level and must be conspicuously identified.


Following Reactivity, look at the Corrosivity (or corrosiveness) of the material. The corrosive class of compounds includes a wide range of organic and inorganic acids/bases, as well as many compounds which can hydrolyze to form acids (e.g., aluminum chloride), and many organic compounds which corrode living tissue through local toxicity mechanisms (e.g., phenol, iodomethane, dimethyl sulfate).

  1. General Rules
    • Shall be stored in secondary containers resistant to corrosion.
    • Shall be stored below eye level.
    • Shall be stored in cool, dry, well-ventilated areas away from sunlight.
    • Some corrosives are also oxidizers or flammable/combustible and must be segregated accordingly.
    • Very weak organic acids may be stored with general organic storage.
    • Store toxic organic corrosives that are not acids or bases per Toxicity guidelines below.
  2. Acids and bases
    • Store in dedicated cabinets appropriate for the properties and must be conspicuously identified with the word “corrosive” and either “acid” or “base”, as appropriate.
      • Do not store hazardous materials in steel cans or drums in the same cupboard as acids.
      • Do not store acids, amines, or ammonia under sinks due to risk of corroding the plumbing.
    • Use secondary containment or separate cabinets to segregate acids from bases, segregate organic from inorganic acids, segregate oxidizing acids from other acids, and segregate organic from inorganic bases.


Finally, consider the toxicity of the material, with particular attention paid to regulated materials. In some cases, this may mean that certain chemicals will be isolated within a storage area. For example, a material that is highly acutely toxic but is also flammable may be stored inside sealed secondary containment in the flammable storage cabinet to protect it against accidental release.

  1. General rules
    • Particularly hazardous substances (PHS) storage areas and work locations are required to be conspicuously identified as to the hazard class by the words “acute toxicant”, “carcinogen” and/or “reproductive toxicant”, as appropriate.
    • Shall not be stored under sinks.

Physical Security

Consider extra physical security such as locked cabinets or restricted room access for highly potent health-hazardous materials, controlled substances, and materials of extreme monetary or scientific value.

  • Store highly toxic chemicals (e.g., cyanides, potent carcinogens, beryllium, liquid mercury) under conditions of satisfactory physical security, preferably in a locked cabinet in a restricted access room.
  • Controlled substances must be segregated and stored as outlined in the Controlled Substances and Precursor Chemicals Program.

Cold Rooms

Cold rooms are not ventilated, therefore:

  • Flammable materials shall not be stored or used in cold rooms.
  • Toxic or other health hazardous materials of sufficient volatility to pose an exposure hazard though the vapor phase shall not be stored or used in cold rooms.
  • Gas cylinders shall not be stored or used in cold rooms.
  • Materials releasing corrosive vapors (e.g., hydrochloric acid, nitric acid) shall not be stored or used in cold rooms.
  • Dry ice, liquid nitrogen, and other materials which may displace oxygen and present an asphyxiation hazard shall not be used or stored in cold rooms.
  • Materials which react with water to produce gases may not be used or stored in cold rooms.

Additional considerations:

  • To prevent mold growth, do not store cardboard or paper materials in the cold room. Please refer to the Mold Prevention in Cold Rooms Fact Sheet for additional information.
  • As most cold rooms are shared spaces, ensure all materials stored in these locations are appropriately labeled with ownership.

Compressed Gas Cylinders

Compressed gas cylinders shall be stored in accordance with the seismic restraint requirements detailed in the Chemical Hygiene Plan (CHP), Section 4, subsection Seismic Safety and Hazardous Materials Storage.

Consideration when working with compressed gases:

  • Ensure all compressed gases are properly stored per regulations and EH&S requirements as noted in the Chemical Hygiene Plan.
  • Ensure incompatible gases are not stored near each other.
  • Ensure cylinders are properly capped when not in use.
  • Add all compressed gases to the chemical inventory in EHSA.
  • Notify labsafety@usc.edu if working with highly toxic or pyrophoric gases.

Seismic Safety and Hazardous Material Storage

The following seismic safety storage guidelines shall be followed to minimize hazardous material storage risk in the event of an earthquake:

  • Liquids which are pyrophoric, toxic, corrosive, sensitizers, carcinogens, or reproductive toxicants shall not be stored above eye level.
    • Other liquids which do not possess significant hazards to the skin, eyes, or health may be stored above eye level, but only if there is no other storage location available, and only if they are in bottles with volume of one liter or less.
  • Solid chemicals which are highly acutely or chronically toxic, significantly carcinogenic, highly reactive, or pyrophoric shall not be stored above eve level.
    • Lower hazard solid chemicals may be stored above eye level, but only if there is no other storage location available and if the container size is one kilogram (1 kg) or less.
  • Ensure open shelves are fitted with appropriate earthquake lips or restraining devices.

Incompatible Chemicals

Handle, store, or pack incompatible chemicals so that they cannot accidentally come into contact with one another. Do not store incompatible chemicals in close proximity to each other. Refer to the ACS for a short list of common laboratory chemicals and the substances with which they are incompatible. Note that this is not an exhaustive list.

Secondary Containment

Secondary containment enhances the safe storage of hazardous materials by the following:

  1. Localize and contain spillage from defective or broken chemical containers.
  2. Prevent incompatible materials from mixing.
  3. Minimize spread of contamination from highly health hazardous materials.

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. Use closed secondary containment, however, to isolate materials exhibiting potent health hazards. All secondary containment shall be clearly labelled with the hazards.