Use of Biological Safety Cabinet in Microbiology
A biological safety cabinet (BSC) is a critical piece of equipment in a microbiology lab, providing a primary barrier to protect three things: the user, the environment, and the sample or product being worked on. It's an enclosed, ventilated workspace that uses a combination of directional airflow and HEPA (High-Efficiency Particulate Air) filters to achieve this protection. This is essential when working with pathogens or other biohazardous materials.
How a Biological Safety Cabinet Works
A BSC operates by creating a curtain of air and using HEPA filters to decontaminate both the air entering the workspace and the air being exhausted.
- Personnel Protection: A constant inward airflow is drawn through a front opening, creating an air curtain that prevents aerosols generated inside the cabinet from escaping into the lab and potentially exposing the user.
- Product Protection: A portion of the air is filtered through a supply HEPA filter and flows downward in a laminar (unidirectional) fashion onto the work surface. This clean, sterile air prevents contamination of the product or sample from "dirty" room air.
- Environmental Protection: All air that is exhausted from the cabinet is passed through an exhaust HEPA filter. This filter traps microorganisms and other particulates, ensuring that the air released back into the laboratory or building is free of biohazardous agents.
Types of Biological Safety Cabinets
BSCs are categorized into three main classes based on their level of protection and airflow patterns:
- Class I: Provides personnel and environmental protection but not product protection. It works by drawing air inward and exhausting it through a HEPA filter. This is suitable for work with low-to-moderate risk agents where product sterility isn't required, such as enclosing equipment that generates aerosols.
- Class II: This is the most common type used in microbiology labs. It provides protection for the personnel, the product, and the environment. It does this by using both an inward airflow at the front and a downward, HEPA-filtered laminar airflow over the work area. Class II cabinets are further divided into types (A1, A2, B1, B2) based on the percentage of air that is recirculated versus exhausted.
- Class III: This is a totally enclosed, gas-tight cabinet (often called a "glove box") that provides the highest level of protection. All operations are performed through attached gloves. This is used for work with high-risk agents that require the highest level of containment, such as those at Biosafety Level 4 (BSL-4).
