TB AII rooms are designed to prevent the spread of droplet nuclei expelled by a patient with TB disease.  AII rooms have the following characteristics:

•AII rooms have negative pressure relative to other parts of the facility.

•Negative pressure causes air to flow from the corridors into the AII room.

•Air cannot escape to the other parts of the facility when the door is closed and the ventilation system is operating properly.

•Air from AII room can be exhausted directly to the outdoors, where the droplet nuclei will be diluted in the outdoor air, or passed through a special high efficiency air (HEPA) filter that removes most (99.97%) of the droplet nuclei before it is returned to the general circulation.

Policies and Practices for Airborne Infectious Isolation in Health-Care Settings