Biosafety level is a feature of risk management assigned to laboratories handling microorganisms belonging to a specific risk group. Biosafety levels range in number from 1 to 4. Level 1 is representative of low risk containment, and 4 is representative of high risk containment. BSL 1 and 2 laboratories have a classical modular design, which show standard ventilation and air change rates. BSL 3 and 4 requires specific design, with attention paid to air flow, air exchange, safety cabinets, personal protective clothing and a certified waste management to handle containments. Organisms handled by BSL 1 and 2 containment laboratories are classed as low risk, in terms of their ability to cause infection and disease in healthy individuals. Bacteria held in high risk (3 and 4) BSL containment labs include TB, SARS and some pathogenic genetically modified organisms.
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