09/11/2009Which is the best containment unit for the laboratory?

There are currently various containment units that can be used for the same application and, ultimately, it falls to the head of the laboratory to decide which unit preferred or which suits the working method and risk assessment and prevention protocol.

To adequately select a containment unit that meets the user's needs, whether a biological safety cabinet or a laboratory isolator, it is imperative to know the applications, the use and the nature of the products that will be processed.

This paragraph aims to provide the decision makers purchasing these units knowledge of the key factors to be able to select the system that most suits requirements:

1. The nature and level of risk of the products to be handled

If the samples are of biological origin, depending on the virulence of the pathogen that is being handled, there are various levels of containment. In order to correctly choose the containment system required, it is essential to know the risk level of the biological agents that are to be handled inside the unit.  These are classified in groups, according to a risk of infection index. 

If the samples are of chemical origin, basically substances that are carcinogenic, mutagenic or toxic for reproduction (other chemical substances are generally handled in gas bells), they cannot easily be neutralised, so they are always handled with a third filtration system under the work surface of the cabinet to protect staff during maintenance work.

2. Protection necessary for...

• The product: If the material being handled inside the cabinet is a product without biological risk that requires conditions of absolute sterility, positive pressure isolators are recommended. If the product does not present chemical or biological risks but needs sterile laminar airflow without conditions of extreme asepsis, it is advisable to work with laminar airflow cabinets instead of isolators due to more favourable ergonomics and the lower capital cost of the unit.

• The user: When level 4 microbiological agents are being handled, it is primordial to guarantee the operator is protected. Under these circumstances it is necessary to use a Class III Biological Safety Cabinet.

• The product, the user and the environment: When working with microorganisms of biosecurity levels 2 and 3, it is important to guarantee the user, the product and the environment are all protected. For these situations, is advisable to use Class II Biological Safety Cabinets. Another option is to use negative pressure isolators. While a cabinet protects the user by means of an air barrier, the isolator is a closed system that protects the user by means of a physical barrier, usually a window.

• The product, the user, the environment and the maintenance staff: When the product to be handled inside the unit is a dangerous chemical substance, such as cytostatic and cytotoxic medicines (substances that are carcinogenic, mutagenic or toxic for reproduction), it is important to protect both the operator and the maintenance staff responsible for changing the filters of the unit when this becomes necessary. On these occasions it is recommend to use a Class II Biological Safety Cabinet or an isolator, both units with a third stage of filtration under the work surface. It is important to take into account that the ergonomics of the user, the access to the work material and the cleaning in a isolator is always much more limited than in a biological safety cabinet due to the fact that operator movement is much more restricted.

3. How many samples can be handled simultaneously?

If the user of the unit intends to handle various samples or products simultaneously, it is important to choose a unit with a sterile laminar airflow system, to minimise the risk of cross contamination between samples. In these cases use Class II Biological Safety Cabinets or isolators should be employed. If only one type of sample will be handled in the cabinet both turbulent and laminar airflow systems can be utilized.

4. Preference for a certified system

To select the appropriate type of unit it is important for the user to understand the governing standards and legislation.

For decades, biological safety cabinets have been regulated by strict legal standards, initially locally (such as BS-5726 in the UK, NF X44-201 in France or DIN 12950 in Germany) and later by a single European regulation, EN 12469. There are several entities such as TÜV and NE which are authorised to issue the corresponding certificate. TÜV in Hamburg has the best reputation for the rigorousness of checks, not only of the units, but also of the traceability of the manufacture.

For isolators, there are no European standards that regulate their design, manufacture and testing procedures for the key values, so if the user needs a certified unit, an isolator would be a more complex option that would require specific validation protocols approved by at least the user, the manufacturer and the endorsing entity of the laboratory.