A biological safety cabinet, or BSC, uses HEPA-filtered laminar (unidirectional) airflow under negative pressure, to protect the user and environment from exposure to airborne biological contaminants.
Biohazard cabinets are regarded as LEV, or Local Exhaust Ventilation control measures under COSHH (Control of Substances Hazardous to Health) regulations, and as such must undergo regular examination and testing to ensure they give continued protection. While this is designed with human safety in mind, in class 2 cabinets it also ensures continued sterility of the product area.
COSHH regulations and user safety
A BSC offers containment by maintaining the interior at negative pressure with respect to the outside environment, with aerosolised contaminants directed away from the user. A single or double HEPA-filtration system ensures the air being exhausted is free of all viable airborne particles. However, regular servicing is required to ensure the cabinet continues to perform safely and efficiently.
To ensure a minimum level of performance and containment, it is a legal COSHH requirement that all microbiological cabinets undergo thorough examination and testing at periods not exceeding 14 months (6 months at Containment Level 3.) This includes examination of HEPA filters; airflow profiling; KI tests, instrument checks and general functional assessment. All tests must comply with BS EN 12469:2000 and results kept for a minimum of 5 years, with a current test certificate on display at all times. Prior to examination, the cabinet must be thoroughly fumigated to render it safe.
Maintaining product sterility
Biosafety booths used solely for protection of, for example, non-hazardous cell cultures are formally exempt from COSHH regulations. However, valuable research can be lost if the work zone becomes contaminated.
The general recommendation is, therefore, that a biological safety cabinet used for product protection should be examined and tested the same way as one used for personnel protection. Where this is not done, the booth must be clearly labelled “Not to be used as a safety cabinet.”