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6. Release a puff of smoke and observe the resulting direction of airflow. Repeat the test at least
once or until consistent results are obtained.

7. Minimize momentum imparted to the smoke by squeezing the bulb or bottle slowly. This will
also help minimize the volume of smoke released.

8. Depending on the velocity of the air through the door undercut, the smoke plume will either
stay disorganized or it will form a distinct streamline. In either case, the smoke will
directionally behave in one of three ways. It will:

a. go through the door undercut into the isolation room,

b. remain motionless, or

c. be blown back into the corridor.

Compliance with the intent of the CDC Guidelines for negative pressure requires that the
smoke be drawn into the isolation room through the door undercut.

9. Release smoke from the corridor side of the door only for occupied TB isolation rooms. If the
room is unoccupied, also release smoke inside the isolation room (same position as in Step No.
5) to verify that released smoke remains contained in the isolation room (i.e., smoke as a
surrogate for TB droplet nuclei).

10. If photography is performed or videotaping, it is recommended that a dark surface be placed
on the floor to maximize contrast. Be aware that most auto focusing cameras cannot focus on
smoke.

Testing “As Used” Conditions:

Testing of negative pressure isolation rooms requires that the test reflect “as-used” conditions.
Consider the following use variables which may affect space pressurization and the performance of
the negative pressure isolation room:

1. Patient toilet rooms are mechanically exhausted to control odors. The position of the toilet
room door may affect the pressure differential between the isolation room and the corridor.
Smoke-trail tests should be performed with the toilet room door open and the toilet room door
closed. This will not be necessary if the toilet room door is normally closed and controlled to
that position by a mechanical door closer.

2. An open window will adversely affect the performance of a negative pressure isolation room.
If the isolation room is equipped with an operable window, perform smoke-trail tests with the
window open and the window closed.

3. There may be corridor doors that isolate the respiratory ward or wing from the rest of the
facility. These corridor doors are provided in the initial design to facilitate space
pressurization schemes and/or building life safety codes. Direct communication with the rest
of the facility may cause pressure transients in the corridor (e.g., proximity to an elevator
lobby) and affect the performance of the isolation room. Perform isolation room smoke-trail

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