In order to maintain a comfortable indoor environment, occupied buildings will feature some form of ventilation and heating / cooling. This may be achieved through natural ventilation (e.g. wind / buoyancy effects), mechanical ventilation (e.g. fans / blowers) or hybrid / mixed-mode (a combination of natural and mechanical) ventilation systems, which due to their differing modes of operation have differing vulnerability to a CBRN attack.
Modern, commercial buildings such as shopping centres, airport terminals and sports venues typically use a distributed (mechanical) heating, ventilation and air-conditioning (HVAC) system managed using a Building Automation and Control System (BACS). HVAC systems, which can have many points of access, potentially provide a viable, rudimentary means of dispersing chemical or biological agents, and so consideration of measures to reduce this risk may need to be considered:
- Review the design and physical security of your air-handling systems, such as access to intakes and outlets
- Improve air filters or upgrade your air-handling systems, as necessary
- Assess the security requirements for the BACS and implement appropriate measures to control access to it
Additionally, areas which may be considered high risk, e.g. mail rooms, may require dedicated air-handling and filtration. Guidance is available on BACS security here.