Optimally, incompatible chemicals such as acids and alkalis should be stored completely separate from one another to prevent mixing in the event of an accidental spill or release of the materials. Limited storage space within the laboratories, however, sometimes prevents such prudent practice of chemical segregation and storage. If space is limited, you can store incompatible chemicals in the same storage cabinet if you segregate the chemicals according to their hazard class and you store them in tubs, trays, or buckets while in the cabinet. These secondary containers reduce the chance that incompatible chemicals will inadvertently contact each other.

Laboratory Hoods

Do not store chemicals in laboratory hoods because the containers may impede airflow and thereby reduce the effectiveness of the hood.

Refrigerated Storage

Store flammable solvents that require storage at reduced temperature (such as isopentane) in refrigerators or freezers designed for storage of flammable liquids. “Safety” refrigerators for flammable liquid storage and “explosion proof” refrigerators are both acceptable. Ordinary household refrigerators are not appropriate for storage of flammable liquids because of interior arcing contacts. Because refrigerators and freezers have no interior space venting, all chemicals should have tightly sealed caps. Apply signage to the doors of chemical refrigerators stating: NO FOOD, BEVERAGE, OR ICE FOR HUMAN CONSUMPTION.”

Figure 4.7
Example sign for a household refrigerator used for storage of lab materials. Flammable storage requires a “safety” or “explosion-proof” refrigerator. This sign is available at the EHS Safety Labels webpage.

Figure 4.8
Sign for entry door to cold room.

Cold rooms have closed air circulation systems that re-circulate escaped vapors within the chamber. The refrigeration coils in cold rooms are aluminum and subject to damage from corrosive atmospheres. The electrical systems normally have vapor proof lights and duplex outlets, but added-on extension cords and plug strips compromise these safety features. Cold rooms are not acceptable for storage of flammables, dry ice, highly toxic liquid chemicals, or compressed gases. If you must refrigerate these chemicals, store them in an approved refrigerator or freezer, rather than a cold room. Post a hazard information sign on the cold room door as illustrated (Fig. 4.8). This sign is also available from the EHS Safety Labels webpage.

Flammable and Combustible Liquid Storage

Fire protection regulations limit the storage of flammable and combustible liquids to 10 gallons (37.9 liters) in open storage, 25 gallons (94.7 liters) in “safety cans”, and 60 gallons* (227.3 liters) in “flammable liquid storage cabinets” per laboratory room. These limits are for the total quantities on hand, including chemicals in storage, chemicals in use, and wastes.

*Note that only 30 gallons (113.6 liters) of Class I liquids are permitted per room. Class I liquids have a flash points less than 100 °F (37.8 °C), and are traditionally known as “flammable” liquids. Most liquids labeled as flammable are Class I liquids. Combustible liquids are Class II or III liquids, and have flashpoints above 100 °F (37.8 °C). Regulations permit up to 60 gallons (227.3 liters) of combustible plus flammable liquids per room, provided no more than 30 gallons are Class I.

Also, the International Fire Code (adopted by the State of North Carolina) places limits on the amounts of flammable and combustible liquids stored in new or renovated buildings as the number of floors above grade increases. For some laboratories located on higher floors in new or renovated buildings, the flammable liquid storage limit per room might be less than 30 gallons. Contact EHS if you have questions about the flammable storage limits for your lab spaces.

Cabinets

You can use cabinets under hoods and laboratory benches for storage of chemicals. In some cases, laboratory furniture manufacturers design cabinets specifically for storage of flammable and/or corrosive materials. However, do not store laboratory chemicals near or under sinks where there may be exposure to water. Storage of cleaning supplies under sinks is acceptable. Cabinets for chemical carcinogens or highly toxic chemicals should have a lock. Regulations of the Drug Enforcement Administration and Bureau of Alcohol, Tobacco, and Firearms require locked storage for controlled substances and some specific explosive compounds (see Chapter 9 for specifics).

Desiccator Jars or Cabinets

Desiccator jars and cabinets are useful for storage of air and water reactive, toxic, and malodorous chemicals. In case of especially malodorous compounds such as mercaptans, replace the desiccator material with a vapor adsorber (e.g. charcoal) to control odors.

Bench Tops and Shelves

Chemical storage on bench tops is undesirable, and is vulnerable to accidental breakage by laboratory, housekeeping, and emergency response personnel. Do not store liquids on shelves that are above eye-level. When storing chemicals on open shelves, consider several factors such as compatibility grouping (see below), the container material (plastic or metal versus breakable glass), physical state of the chemical (it’s riskier to store liquids on open shelves compared to solids), the relative toxicity of the chemical, and the height and depth of the shelving.