As mentioned earlier, aerosol-tight caps (for swing-out buckets) or aerosol-tight lids (for fixed-angle rotors) are essential for centrifuging hazardous samples. The following points outline proper handling and maintenance of the equipment:
- Loading and unloading. Aerosol-tight caps and lids do not prevent formation of aerosols during centrifugation; rather, they ensure aerosols cannot leak from the closed system. Therefore, you must wait at least 10 minutes before opening the bucket or rotor. This gives the aerosols time to settle down. Also, you should load and unload the buckets or rotor in a biosafety cabinet (especially in virology and mycobacteriology) to minimalize the risk of escaping aerosols.
- Disinfection and autoclaving. Buckets, caps, rotors, and lids are the main components that come into contact with aerosols. Correctly handling them does prevent aerosols from being dispersed within the rest of the device, but the parts themselves do need to be disinfected after each use. This is done using suitable disinfectants and following to the manufacturer’s recommendations (usually 70% ethanol works fine for rotors and buckets). You can also regularly autoclave rotors, rotor lids, buckets, and caps (please refer to the operating manual for parameters; autoclaving is usually carried out for 20 minutes at 121°C, 2 bar).
- Seals. All aerosol-tight caps and lids are delivered with rubber seals. Together, the caps and seals form an aerosol-tight unit, which must be tested and certified by an independent test institute (e.g., Public Health England, Porton Down, UK). You need to regularly check the seals to ensure they are intact, nonporous, and correctly seated in the grooves. If any of these factors are not present, aerosol-tightness cannot be guaranteed. If necessary, grease or even replace the rubber seal.
Using centrifuges in a safe way
The centrifuge itself is another factor to be considered in the safety workflow:
- Speed limits. Exceeding the speed limits of rotors can lead to tube breakage or even a rotor crash, therefore the rotor speed limit must be considered when the centrifuge is not equipped with automatic rotor recognition (a feature that ensures the maximum speed is not exceeded).
- Tube breakage. Should a tube break or leak, do not open the centrifuge for at least 30 minutes after the run. Since this cannot always be detected before you open the buckets or rotor (a sudden imbalance can be a first sign of tube breakage), we recommend waiting at least 10 minutes at all times before you open the containers.
- Maintenance. Good maintenance and regular checks of the centrifuge, rotors, and equipment is necessary for ensuring safety and preventing system failure (e.g., rotor crash, which leads to a large amount of aerosol escaping with the centrifuge exhaust). Please refer to the manufacturer’s instructions for maintenance information or watch our centrifuge maintenance video.
Personal protective gear is another crucial factor in avoiding contact with infectious or harmful substances (mostly through ingestion and dermal contact) and the following should be heeded:
- Protective gear. Always wear a laboratory coat, safety gloves, and safety goggles when working with infectious or hazardous substances. This will minimize the risk of dermal or mucous contact with the material (splatter, droplets, etc.)
- Clean hands. After working with infectious material, remove the used gloves and disinfect your hands before washing them thoroughly.
- Clean gear. Be sure personnel protective gear, including laboratory coats, safety goggles, and the like, are regularly cleaned; replace if damaged.
Including these precautions in the workflow will provide a higher level of security during centrifugation as well as minimize the risk of LAIs.References: https://www.cdc.gov/Mmwr/preview/mmwrhtml/su6101a1.htm
(Guidelines for Safe work Practices in Human and Animal Medical Diagnostic Laboratories)
Book: Collins & Lyne's Microbiological Methods (8th Edition, Arnold, 2004, Chapter 1, Safety in microbiology)