A biosafety cabinet is a ventilated laboratory workstation that helps protect people, samples, and the environment when handling biological materials. It is important in medical technology because many tests, cultures, and research procedures involve droplets or aerosols that can carry microbes. The cabinet does not make risky work harmless, but it greatly reduces exposure when used with correct technique.
Its safety depends on controlled airflow, filtration, and keeping the work opening unobstructed.
Inside a common Class II biosafety cabinet, room air is pulled inward through the front opening to protect the worker, while filtered downward airflow protects the sample from contamination. Air is moved by a blower through HEPA filters, which trap very small particles before air is recirculated or exhausted. The front grille, sash height, and internal airflow balance are all designed to maintain a stable protective air curtain.
If the airflow is blocked by arms, equipment, or fast movements, the cabinet can lose containment even while the fan is running.
Key Facts
- A Class II biosafety cabinet protects the worker, the sample, and the environment using controlled airflow and HEPA filtration.
- HEPA filters remove at least 99.97% of particles with diameter 0.3 micrometers under standard test conditions.
- Face velocity is the average inward air speed at the front opening, often measured in ft/min or m/s.
- Flow rate is related to area and speed by Q = A v.
- Many cabinets use vertical laminar downflow to sweep clean filtered air over the work surface.
- The sash must be kept at the certified working height because changing the opening changes airflow patterns and containment.
Vocabulary
- Biosafety cabinet
- A ventilated enclosure designed to reduce exposure to biological aerosols during laboratory work.
- HEPA filter
- A high efficiency particulate air filter that captures tiny airborne particles using a dense fiber mat.
- Laminar airflow
- Smooth airflow in mostly parallel layers that reduces mixing and helps maintain a clean work zone.
- Face velocity
- The average speed of air moving into the front opening of a biosafety cabinet.
- Sash
- The movable front window that sets the cabinet opening and helps control airflow.
Common Mistakes to Avoid
- Using a biosafety cabinet like a chemical fume hood is wrong because many cabinets recirculate some air and are not designed for large amounts of volatile chemicals.
- Blocking the front or rear grilles is wrong because it disrupts inward and downward airflow, which can let aerosols escape or contaminate the sample.
- Moving hands quickly in and out of the cabinet is wrong because sudden motion can create turbulence that breaks the protective air curtain.
- Working with the sash above or below the certified height is wrong because the cabinet was tested for safe containment at a specific opening.
Practice Questions
- 1 A cabinet front opening has an area of 0.42 m^2 and an average inward air speed of 0.50 m/s. Use Q = A v to find the airflow rate in m^3/s.
- 2 A HEPA filter removes 99.97% of test particles. If 2,000,000 particles reach the filter, how many particles are expected to pass through?
- 3 Explain why placing a large centrifuge tube rack over the front grille can reduce protection for both the worker and the sample.