The recommended way to control TB as an airborne infection, is via two important measures:

1. The use of administrative measures to reduce the risk for exposure to persons who have infectious TB; or

2. The use of engineering controls to prevent the spread and reduce the concentration of infectious droplet nuclei.

The first, administrative measures, is quite obvious to most healthcare workers, it is to keep people away from the infection, but what happens when the person with that infection needs to be tested or cared for. Or the worker is in a business that has contact with people that are unknown if they have TB or not. The healthcare worker needs to not only protect themselves but to also protect other patients from getting the infection as well. This brings us to the second point, a hierarchy of engineering control measures.

1. Use facility heating, ventilating and air conditioning systems ( HVAC )to reduce the concentration of airborne tubercle bacilli in the air. If this is not possible then;

2. Install room air high efficiency particulate air ( HEPA ) recirculation system, plus

3. Ultra violet germicidal irradiation may be used as a supplement to ventilating methods.

4. Portable air filters may vary in effectiveness due to the placement of furniture, where the people are, and the overall configuration of the room.

The use of the facility HVAC systems is typically quite expensive and in fact may not give as good a result as a recirculation system mounted directly in the space. The reasons that the facility HVAC system may not be as good are:

1. The facility HVAC system may not be able to get enough clean air to the space, it is recommended that 12 air changes be used. Increasing air flows in building systems usually is impossible or very expensive.

2. The facility HVAC system may not distribute and mix the air very well, return air should be at the floor and supply air at the ceiling level. This is the way an operating room system is designed.

3. The room HEPA recirculation system is able to set up the best air flow patterns because of its design and puts far more clean air into the space, a 16’ x 16’ room with an 8’ high ceiling will get at least 12 air changes with a nominally 400 CFM HEPA recirculation system.

4. Setup negative pressure, isolation rooms where TB is suspect. This is a very expensive affair with a facility HVAC system. Very simple for a room HEPA recirculation system as the top is simply changed from a full top recirculation grille to a grille with a circular duct connector (usually 10" diameter).

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