Critical ventilation systems for the safe handling of dangerous pathogens

“Containment laboratories must be designed and built so as to prevent or control the exposure of laboratory workers, other persons and the environment to the biological agent in use.” Medical Research Council: Standards for Containment Level 3 Facilities

As an expert in the provision of critical ventilation systems for healthcare and life sciences facilities, Medical Air Technology (MAT) supports research into hazardous pathogens by providing CL3 laboratories (also known as Category 3 or Cat 3 laboratories) for some of the UK’s leading research facilities, including:


  • Liverpool School of Tropical Medicine
  • Glan Clwyd Hospital, North Wales
  • Imperial College London
  • Queen Mary University of London
  • Royal Liverpool Hospital
  • Cambridge University’s Department of Chemical Engineering and Biotechnology


Our turnkey design-and-build solutions for CL3 laboratories provide a fully compliant facility with integrated ventilation systems.  The laboratories are easy to clean and maintain, designed in accordance with ACDP and SAPO guidelines, and packed full of features to fulfil each client’s specific needs.


What is a CL3 Laboratory?

A CL3 laboratory is required when handling human pathogens that may be transmitted via inhalation, that often have a low infectious dose to produce effects and that can cause serious or life-threatening disease. These pathogens include HIV, hepatitis B, yellow fever and rabies.  

CL3 containment features primary and secondary barriers to minimise the release of infectious organisms into the immediate area and the environment. Every CL3 laboratory has two physical layers of containment:

  • The primary barrier (safety equipment), which contains the hazard at source
  • The secondary barrier (the laboratory itself), the design of which is essential in protecting both the worker and those outside the laboratory and also restricts entry.

Conceptualising and designing a safe and compliant CL3 laboratory requires expert knowledge and a thorough and advanced understanding of the way airflow operates and the importance of room structure. MAT’s energy efficient laboratory critical ventilation system provides the secondary barrier necessary to provide containment.

Specialist airflow design ensures the maintenance of constant negative pressure and door protection to stop the escape of hazardous pathogens.  This is achieved using a monitored pressure control system, through which air is supplied to the lobby and drawn through the facility by a combination of safety cabinet extract and HEPA filtration of exhausted laboratory air. The lobby provides an additional level of control of the flow of air into the laboratory when workers are entering or exiting, avoiding potentially problematic fluctuations in air patterns within the laboratory. 

In addition, the laboratory is an air- and gas-tight, leak-proof room. This is essential not only for the containment of pathogens, but also to ensure that room fumigation, which uses highly toxic concentrations of formalin (formaldehyde), can be carried out safely. 

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