Tips for Aseptic Technique in the Laboratory – Biosafety Cabinets (Part 4 of 4)

Cara N. Wilder, Ph.D.

When working with hazardous or sterile materials, it is recommended that all associated procedures are performed in a biosafety cabinet. These apparatuses are enclosed, ventilated workspaces designed to protect laboratory personnel and materials from cross contamination during routine procedures. Generally, work spaces within the biosafety cabinet are protected through the use of a high-efficiency particulate air (HEPA) filtration method, which removes harmful microbes from the air.

There are three types of biological safety cabinets: Class I, Class II, and Class III.

Class I: These biological safety cabinets are open-front negative pressure systems with HEPA filtration systems. These biosafety cabinets provide protection for laboratory personnel and the environment, but will not provide product protection. These cabinets are often used to enclose specific equipment or procedures that may generate potentially hazardous aerosols.

Class II: These biological safety cabinets are open-front, ventilated, laminar-flow cabinets. These provide HEPA-filtered, recirculated airflow within the work space. Class II cabinets provide protection to laboratory personnel, the environment, and to products by drawing a curtain of sterile air over the products that are being handled. These cabinets are commonly used in microbiology laboratories working with non-infectious agents (Biosafety Level 1 or 2) as they protect the contained materials from extraneous airborne contaminants.

Class III: These biological safety cabinets are totally enclosed, ventilated systems with gas-tight construction. These cabinets are used through attached rubber gloves. Generally, the air supply is drawn into the cabinet through HEPA filters, and the exhaust air is filtered by two HEPA filters installed in a series. This biosafety cabinet system is commonly used with high-risk infectious agents (Biosafety Level 3, 4, or 5) to prevent the escape of aerosols.

Below, we describe some tips on how to properly use a Class I or Class II biosafety cabinet when working with non-infectious materials.

Keeping a Biosafety Cabinet Safe

·         Certify all biosafety cabinets upon installation

·         Routinely test the quality of airflow

·         Ensure the integrity of filters

·         Biosafety cabinets should be approved by the resident Biosafety officer

·         Ensure that all biosafety cabinets are routinely recertified

Biosafety Cabinet Sanitation

·         Clean work surfaces with 70% ethanol before and after use. When using 70% ethanol, ensure that there are no open flames nearby.

·         If the biosafety cabinet is equipped with germicidal UV lights, decontaminate work surfaces before and after use by turning on the UV light for at least 15 minutes. Never use the UV light while the biosafety cabinet is in use.

·         Routinely remove any biohazard waste from the biosafety cabinet.

·         Using an appropriate disinfectant, such as 70 % ethanol, wipe down the outer surface of all pipettes, pipette tip boxes, media, materials, etc. prior to placing them in the biosafety cabinet.

·         Always wear a clean lab coat and sterile gloves when working in a biosafety cabinet.

Proper use of a Biosafety Cabinet

·         Turn on the biosafety cabinet 15 minutes prior to use.

·         Only raise the biosafety cabinet sash to the recommended level, this will reduce disruption to the air flow as well as assist in the prevention of airborne contaminant entry.

·         When using a biosafety cabinet, limit the amount of movement in the cabinet and do not remove your arms. Additionally, limit the access to the area around the biosafety cabinet. This will reduce disruption to the airflow.

·         Do not use open flames within a biosafety cabinet. The resulting heat from the flame can disrupt the air flow provided by the biosafety cabinet, increasing the risk for contamination. Additionally, gas leaks associated with Bunsen burners or the use of an alcohol-based disinfectant near an open flame can result in fire or injury.

Stay clean, and happy culturing!