Choosing the Right Microbiological Safety Cabinet

The function of a microbiological safety cabinet (MSC) is to protect users and the environment from contaminants and dangerous microorganisms. They are used in laboratories to prevent exposure to potentially harmful aerosols when handling samples and reagents. Some also make it possible to avoid contamination of the samples handled. They therefore meet three main objectives: protection of personnel, protection of the environment, and protection of the products handled. They are also known as biosafety cabinets (BSCs) and biological safety cabinets.

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What are the different types of microbiological safety cabinets?
According to EN 12469, there are several classes of biological safety cabinets, depending on the level of protection they offer.
- Class I: This cabinet has an opening at the front. The air from the laboratory is filtered and sucked into the cabinet towards the product to be handled. This airflow prevents contaminants from escaping but does not protect the product. Class I MSCs are designed to ensure operator safety and environmental protection.
- Class II: This cabinet has a front opening and uses a downward flow of filtered air. This acts as a barrier to prevent contaminants from escaping and minimizes the risk of product contamination. There is, however, a risk of contaminants escaping due to the location of the suction grille, which results in less air flow at the top than at the bottom. As well as protecting the operator and the environment, these cabinets preserve the integrity of the sample being handled. Class II cabinets are divided into three subcategories:
  
  Type A
  
  Type B
  
  Type C
- Class III: This cabinet is totally enclosed. It thus offers a sealed working area. As a result, the protection of personnel, samples and the environment is virtually total.
Nuaire Class I MSC

Biobase Class II MSC

LAMSYSTEMS Class III MSC

No matter the cabinet, the air expelled into the atmosphere is filtered to avoid the risk of contamination. An important factor to consider is the degree of harmfulness of the biological agents handled, which will determine the class of device to be used.
The three main classes and their respective levels of protection:
- Class I: Protects the operator and the environment, but not the products handled.
- Class II: Restricts the escape of contaminants and contamination of the products handled.
- Class III: Offers almost total protection for the operator, the environment, and the products handled.
Where are microbiological safety cabinets used?
MSCs are indispensable in any environment where it is necessary to contain contaminants that are harmful to the operator, the environment, and the products handled. These contaminants can take two physical forms: particles (such as dust, viruses, bacteria, etc.) or gases. They result from the handling of biological products containing potentially airborne pathogens.

MSCs are mainly used in various types of laboratories:
- Analysis laboratories
- Quality control laboratories
- Research laboratories
- Teaching laboratories
What are the different types of filtration systems in microbiological safety cabinets?
The filtration system varies according to the type of cabinet and contaminant. Let’s take the example of particulate and gaseous contaminants.
- Filtration of particulate contaminants: To retain potentially contaminated particles, filters usually composed of fibers are used. These need to be changed regularly for greater efficiency and safety. The filter’s efficiency is assessed in accordance with EN 1822.
- Filtration of gaseous contaminants: This is ensured by several layers of filtering material, such as activated carbon. There is no universal filter. Your choice will depend on the nature of the gases or vapors. Each one has a certain retention capacity, beyond which it ceases to be effective.
How do you ensure that a microbiological safety cabinet works properly?
Certain precautions are essential to ensure the effective and safe operation of MSCs, such as checking the performance of filters and the air system.
- Filter condition: It is crucial to periodically inspect the MSC’s filters and change them as soon as necessary.
- Air system: The air exhausted from the cabinet, once filtered, can be expelled outside the building (exhaust) or reintroduced into the laboratory environment (recirculation). If the recirculation mode is not working properly, there is a great risk of contaminating the working environment.
- One operator per MSC: For safety reasons, it is not recommended that several operators work on the same MSC at the same time.
What aspects should be taken into account when installing a microbiological safety cabinet?
The installation of a biosafety cabinet must meet certain basic requirements.
- The MSC must be located away from passageways and any elements that could compromise the stability of the cabinet’s airflow, such as windows, doors, pillars, or partitions.
- Benchtop MSCs must have an adequate load capacity (around 200 kg).
- You should also check the space available, as MSCs are relatively large pieces of equipment.
- When the exhaust air from the CSB has to be led outside the premises, make sure it is possible to connect the cabinet to the building’s exhaust system.