Before choosing which type of biological safety cabinet is most suitable for the handling of potentially pathogenic material, consideration must be given to the advice from the UK’s Advisory Committee on Dangerous Pathogens.

  • Group 1 – A biological agent unlikely to cause human disease.
  • Group 2 – A biological agent that can cause human disease and may be hazardous to employees; it is unlikely to spread to the community and there is usually effective prophylaxis or effective treatment available.
  • Group 3 – A biological agent that can cause severe human disease and presents a serious hazard to employees; it may present a risk of spreading to the community, but there is usually effective prophylaxis or treatment available.
  • Group 4 – A biological agent that causes severe human disease and is a serious hazard to employees; it is likely to spread to the community and there is usually no effective prophylaxis or treatment available.

To deal with these different threat levels, three classes of Microbiological Safety Cabinets (MSC’s) have been developed.

Class I MSC 

The Class I MSC sucks air into the cabinet and away from the operator in order to generate a very high level of protection. All exhaust air must pass through a filter before it is released to the atmosphere.

High Efficiency Particulate Air (HEPA) filters are fitted immediately above the working area. Suitable for material in groups 1 – 3, the Class I cabinet would be used typically in laboratories where patient specimens are handled prior to the identification of any disease.

Class II MSC

Suitable for Group 1-2 materials, and Group 3 at the discretion of the Lab Safety Officer, the Class II Biological Safety Cabinet offers a high degree of operator protection by drawing laboratory air quickly around and past the operator. The Class II also attempts to protect the integrity of the material under investigation.


Although the Class I and Class II MSC’s generate a high measure of protection for their operators, this is not absolute. When working with Group 4 materials, a Class III MSC guarantees maximum security for the operator and the laboratory.

Similar to a Class I however, operators must access the work surface and samples via sealed glove ports. All materials must be transferred in and out of the cabinet through a transfer hatch. Exhaust air is pulled through one or more HEPA filters to the atmosphere via a ducted exhaust fan and make-up air is drawn into the cabinet via a HEPA filter.

Finally, these cabinets are also usually sited in a purpose built, high biological security laboratory to ensure every eventuality is covered in attempting to make sure that the material under investigation cannot escape to harm the operators or the outside world.

Our guide to the types of biological containment cabinets available to help you build a safe working environment has given you an awareness of the strengths and weaknesses of each type. Knowing how to apply these principles in your own working environment may not be so straightforward.

For more information on how our Market Leading Clean Air Solutions can benefit you, contact Monmouth Scientific’s Technical Sales Experts on;+44(0)1278 458090 or email [email protected].