Biosafety cabinets

A biosafety cabinet class I is a laboratory workstation that is used to protect the user against biohazards. The cabinet has a unidirectional upwards airflow and sucks the air trough a HEPA filter before re-sending it into the laboratory environment. Due to the flow direction, unfiltered air is passing by the product/experiment used inside the cabinet. In practice, for most applications involving biohazards, the cross contamination with unfiltered air is a problem. That is why the biosafety cabinet class I has almost disappeared from the lab environment. Besides the problem of cross contamination, the cost of the cabinet is more or less the same as the cost of a biosafety cabinet class II type A2, which does offer protection of the product/experiment against air contaminants.

A biosafety cabinet class II is a laboratory workstation providing user and environment protection against biohazards AND providing protection of the product/experiment against air contaminants. The European standard allows the users to choose which type of class II cabinet they use, as long as it complies with certain test criteria. In practice, a biosafety cabinet class II type A2 is used for around 95% of applications involving biohazards within Europe.

When low concentrations of chemicals are used in a class II A2 biosafety cabinet, it is in most cases connected to the laboratory HVAC system using thimble ducting. The flow rate just needs to be above a certain minimum and does not need to be regulated exactly. An alternative is adding a carbon filter on top of the exhaust filter, but this technology is not used a lot yet in biosafety cabinets. The only limitation of a biosafety cabinet class II type A2 is when you use large quantities of volatile chemicals in the same workstation as biohazards. Because a class II A2 re-circulates 70% of the air, there is the possibility that chemical vapours build up. When these are toxic or explosive, they can be a large safety risk. In this case the other types of the American standard are better solutions. Biosafety cabinets class 2 type B1, B2 and C1 are all biosafety cabinets that are developed to work with large quantities of volatile chemicals in the same cabinet where biohazards are used. They are connected to an HVAC system. The flow rate needs to be regulated very exactly for these 3 types of cabinets using hard ducting. In practice this means an individual HVAC system with an individual FAN unit needs to be installed in the laboratory dedicated for these cabinets. This makes the installation a lot more expensive and complex compared to a type II A2. The scope for a biosafety cabinet class II type B1, B2 and C1 is exactly the same. In practice laboratories will never choose type B1 and C1 because they have the same cost as a B2, but use of chemicals is limited to certain parts of the work area.

                                      
A biosafety cabinet class III is a laboratory workstation that protects the user and environment against biohazards and the product/experiment against air contaminants. The main difference with a biosafety cabinet class II is that there is a complete physical separation between the user and the product/experiment, while a class II has a sash opening. It is also sometimes referred to as an isolator, but this name is used also for some other cabinet types. Materials need to be entered via an air sash, and the manipulations are done using long gloves that are integrated into the front window. This type of cabinet is usually only found in biosafety level 4 laboratories.

If you use small amounts of chemicals, you can use a biosafety cabinet class II A2. You just need to connect it to the HVAC system using an exhaust collar and ducting. The flow rate needs to be above a threshold communicated by the supplier of the cabinet. An alternative for ducting is using a carbon filter. Carbon filters have coatings that can capture chemicals using a process called adsorption. When using large volumes of volatile chemicals in the same workstation as biohazards, you need to keep in mind that a biosafety cabinet class II A2 has 70% re-circulation. This can cause build-up of chemical vapours inside the workstation and create a risk. If a biosafety cabinet class II A2 is not an option for that reason, the biosafety cabinet class II B2 is the best solution.

It is very confusing for the end users to find the right type of biological safety cabinet. This is related to the presence of 2 different standards :

• First of all, there is the older NSF 49 standard from the US. This standard only talks about class II biosafety cabinets and defines 4 types based on their construction.
• There is also the newer European EN 12469 standard. This standard defines 3 classes of biosafety cabinets but does not define how they need to be built. They just need to pass certain test criteria.

In Europe, we need to follow the European standard of course. In practice, for most applications a class II biosafety cabinet will be needed. Taking into account that the European standards do not say much about the construction, you can choose from all types defined by the US standard. In practice, we see that around 95% of the biosafety cabinets in the Benelux are class II A2. Why is that?

Analis, as an exclusive distributor of Esco for the BeNeLux, also offers the necessary support. We have a local service team for installation, validation, preventive, and corrective maintenance.