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TB Questions and Answers - Section 3d

Containment Dilution By Using Negative Pressure


Q: I've been told that a negative pressure room helps to control TB bacteria. What constitutes a negative pressure room?

A: A room is said to be under negative pressure when more air is exhausted from the room than is being supplied to it.

Q: How does this help to control TB contaminants?

A: Direction of air flow is determined by the differences in air pressure between adjacent areas, with air flowing from high pressure areas to lower pressure areas. If a TB patient's room is under lower (or negative) pressure to adjoining areas, the contaminated air should not be able to flow to the uncontaminated adjoining areas.

Q: Is it easy to maintain negative pressure in a room?

A: Proper air flow and pressure differentials between areas of a health care facility are difficult to control because of open doors, movement of patients and staff, temperature, and the effect of vertical openings. Air pressure differentials can best be maintained in completely closed rooms. An open door between two areas may reduce any existing pressure differential and could reduce or eliminate the desired effect.

Q: Does a room under negative pressure protect these providing care within the contaminated room?

A: This depends on the volume of air being exhausted from the room and the frequency at which it is removed. The only protection provided to those within the room is contaminant removal by exhaust.

Q: Is there any way to increase the protection of those within the contaminated negative pressure rooms?

A: An air purifier providing supplemental contaminant removal and air changes could be employed. UV lamps may also provide some additional protection.

Q: How many air changes are recommended for negative pressure rooms being used for TB patients?

A: The CDC recommends that there be at least six total air changes per hour, and at least two outside air changes per hour within room air distribution to dilute or remove TB bacillus from locations where health care facility personnel or visitors are likely to be exposed.



-End of Section 3d-

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