Aerosolization

Aerosols are liquid and solid particles suspended in the air. An aerosol with a diameter of 5 microns or less can remain airborne for a long period of time, spread wide distances, and is easily inhaled. Particles with a diameter larger than 5 microns tend to settle rapidly and can contaminate skin, ventilation systems, and other surfaces. Over the years, there have been many documented cases of lab personnel acquiring diseases due to their work with infectious agents. Approximately 80% of these cases are assumed to be primarily related to the creation of aerosols in the lab. Whenever work with potentially infectious agents is performed, appropriate measures must be taken to protect workers and the environment.

• Centrifuging
• Grinding
• Blending
• Vigorous shaking or mixing
• Sonic disruption
• Opening containers with high internal pressures
• Inoculating animals intranasally
• Harvesting tissues from animals or embryonated eggs
• Pipetting

Laboratory workers should learn and follow (as appropriate) these practices. Using the appropriate safety equipment and following safety procedures are the primary methods 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 workers from aerosols, if working with RG2 or higher agents. Other safety devices include safety centrifuges with automatic locking mechanisms or solid lids, safety centrifuge cups, safety blenders, and safety sonicators.
• 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 specially designed 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 MUST BE 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.
• Wear gloves when handling infectious materials, or infected animals. For animal work follow CDC Biosafety in Microbiological and Biomedical Laboratories animal biosafety level criteria.