This blog post describes steps teachers should take to ensure that laboratory freezers and refrigerators are free from safety hazards. Science teachers should adhere to the following standard operating procedures, via the University of Texas at Austin.

• Designate one employee to oversee the laboratory refrigerator and freezer.
• Do not store food in refrigerators or freezers that store chemicals.
• To avoid biological and chemical cross-contamination, do not store food and beverages with bacteria plates, chemical solutions, and specimens in the same refrigerator.
• Clean out refrigerators and freezers on a regular basis.
• Seal/cap, securely place, and label containers stored in the refrigerator or freezer. Do not use aluminum foil, corks, and glass stoppers as caps for containers.
• Store all liquid chemicals in plastic trays.
• Appropriately label all stored items.
• Regularly review the inventory of refrigerators and freezers to ensure the contents are compatible.
• Know the shelf life and amount of stored chemicals. Each chemical contains decomposition products that could be hazardous over time.
• Power outages and technology failures can affect stored contents. Watch out for unusual odors and vapors from chemicals after such an event.
• Inspect the appliance at least once per month.
• Post an up-to-date inventory on the refrigerator door.
• Properly install the refrigerator, making sure that it is grounded. No extension cord should be used.
• Place the refrigerator and freezer away from lab exits.

Decontaminating fridges and freezers

The following list describes safety protocols for decontamination of the refrigerator and freezer in the event of a spill or break.

• Non-hazardous items: Empty and defrost non-hazardous items. Clean up any spills or leaks of non-hazardous material with soap and water and paper towels.

• Chemicals: Remove all items and defrost. Clean chemicals spills or leaks with the appropriate solvent (e.g., isopropyl alcohol or soap and water and paper towels). Check the Safety Data Sheet (SDS) for each chemical and dispose of used cleaning materials properly.

• Biological agents: Remove all items and defrost. Clean biological agents that have spilled or leaked with a 10% bleach solution and paper towels (one part bleach to nine parts water). Dispose of used cleaning materials properly.

• Combination of chemicals and biological agents: Remove all items and defrost. If any chemicals and/or biological agents have spilled or leaked, follow the aforementioned protocols. Be careful not to combine incompatible substances such as bleach and ammonia. Dispose of the agents properly and used cleaning materials.

• Radioactive material: If a spill involving radioactive material and any combination of radioactive material with chemicals or biological agents should occur, contact your local or state radiation officer immediately.

Cool alternatives

There are several alternative refrigerators and freezers for safer storage of laboratory materials. If you’re planning on storing aqueous solutions and nonflammable and nonexplosive materials, a regular household refrigerator and freezer could suffice in the school science lab or preparation room. If you’re planning on storing flammable or potentially explosive materials, use a lab-safe, explosion proof refrigerator or freezer.

In areas where the air outside the refrigerator could be explosive such as in a chemical storeroom or prep room, explosion-proof refrigerators and freezers provide the best protection. Explosion-proof refrigerators and freezers do not have internal switching devices that can arc or spark as an ignition source. In addition, the compressor and other circuitry are generally located on top of the unit to reduce the potential for igniting floor-level flammable vapors. Special inner shell materials inside explosion-proof refrigerators and freezers control or limit damage should an exothermic reaction occur within the storage compartment involving liquids, gases, or solids with flashpoints of less than 100°F (38°C).

Explosion-proof refrigerators feature enclosed motors to eliminate sparking and bear an FM (Factory Mutual) or UL (Underwriters Laboratory) explosion-proof label. Such refrigerators must meet the requirements for the Class 1, Division 1 Electrical Safety Code (NPFA 45 and NFPA 70) and require direct wiring to the power source via a metal conduit. Storage requirements also apply to any solution or specimen that may release flammable fumes. Explosion-proof refrigerators and freezers cost between $4,000 and $11,000.

Moreover, freezers in science labs should be frost-free, preventing water drainage or damage. The refrigerator or freezer should also meet all applicable codes. For more information, visit: http://productspec.ul.com/document.php?id=SOVQ.GuideInfo.

Follow the signs

Refrigerators and freezers are required to have the following signage.

• “Edible Food and Drink Only” or “Non-flammable/Non-explosive Solutions Only” signs should be placed on the outside of personal refrigerators and freezers. A sign stating “Unsafe for Flammable Storage” should also be present on the exterior surface of the unit.
• Explosion-proof refrigerators and freezers should have signage stating: “Safe for Flammable Storage.”
• Refrigerators and freezers storing radioactive materials must be clearly labeled: “Caution, Radioactive Material. No Food or Beverages May Be Stored in This Unit.”

Free safety signage print-outs can be found here.

More information

Safety Data Sheets (SDSs) provide information relative to the need for cooling or freezing chemicals for storage or extended life. Equally important is information provided on hazardous decomposition products produced over time. Additional information can be secured from manufacturers.

Submit questions regarding safety to Ken Roy at safersci@gmail.com or leave him a comment below. Follow Ken Roy on Twitter: @drroysafersci.

NSTA resources and safety issue papers
Join NSTA
Follow NSTA