Preventing Aerosol Production

Examples of Aerosol-Producing Activities in the Lab

• Carelessly removing gloves
• Pouring liquids
• Removing (“popping off”) stoppers
• Opening lyophilized cultures, snap top tubes, bottles
• Blowing out pipettes
• Shaking or vortexing open tubes, stirring
• Dropping/breakage of culture containers
• Flaming inoculating needles, loops, or slides
• Inserting a hot loop into a culture
• Pulling needles out of septum, filling a syringe
• Centrifugation steps such as filling centrifuge tubes, removing plugs or caps from tubes after centrifugation, removing supernatant, resuspending sedimented pellets, breakage of tubes during centrifugation, and centrifugation itself
• Sonicating, homogenizing, blending, grinding, cell disruption with French press
• Cell sorters
• Vacuum and aspirating equipment
• Intranasal inoculation of animals
• Cage cleaning, changing animal bedding
• Harvesting infected material from animals, eggs, and other virology procedures
• Necropsies of infected animals

Safe Work Practices to Minimize the Creation of and Exposure to Aerosols

Lab Safety Equipment to Protect Personnel from Aerosols

• A certified biological safety cabinet (class I or II) is the primary barrier to protect worker from aerosols if working with RG2 or higher agents
• Centrifuges with safety centrifuge cups
• Vacuum line trap and filter systems are used to protect the vacuum system from aerosols

Safe Work Practices for Centrifugation

• Routinely inspect centrifuge to ensure that leakage is not occurring
• Do not overfill centrifuge tubes. Wipe the outside of the tubes with disinfectant after they are filled and sealed
• Centrifugation may be performed in a centrifuge that is contained within a biological safety cabinet or other physical containment device
• If a whole centrifuge containment device is not available, internal aerosol containment devices (e.g., sealed canisters, safety cups or buckets with covers, heat sealed tubes or sealed rotors, etc) should be used
• Aerosol containment devices should be removed from the centrifuge and opened in a biological safety cabinet. If a biological safety cabinet is unavailable, a minimum of 10 minutes settling time should be allowed before opening

Safe Work Practices for Blending, Sonicating, Grinding, and Lyophilizing

• Operate blender, sonicator, and grinder in a biological safety cabinet, or place a towel moistened with disinfectant over the top of blender, grinder, or sonicator
• Use safety blenders designed to prevent leakage
• If leak-proof blender is not available, regularly inspect the bottom of the blender for leakage
• Avoid glass blenders
• Allow aerosols to settle for at least 5 minutes before opening blender
• Filter lyophilizer vacuum pump exhaust through HEPA filters or vent into a biological safety cabinet
• Autoclave or disinfect all equipment promptly after use

Safe Work Practices for Pipetting

• Drain a pipette with tip against the inner wall of the receiving vessel. Never forcibly expel any hazardous material from a pipette
• Carefully eject the disposable pipette tips to minimize aerosol formation. A wetted towel in the bottom of the dispensing container (which is often a glass beaker) will keep the pipette tip from bouncing around in the container, thereby minimizing aerosol production
• Place reusable pipettes horizontally in a pan filled with enough liquid disinfectant to completely cover them
• Mouth pipetting is prohibited; mechanical pipetting devices are used

Other Safety Precautions

• Minimize air bubbles when filling a syringe. Place a pad moistened with disinfectant over the tip of the needle when expelling air
• Use a shielded electric incinerator or hot bead sterilizer to sterilize inoculating loops. Disposable plastic loops and culture needles are good alternatives to open flames
• If a spill occurs that may generate aerosols, leave the area, close the door, wait 30-60 minutes to allow dissipation of aerosols. See the GW biosafety manual for spill cleanup
• Wear gloves when handling infectious materials, or infected animals