Basic Documentation

Room Pressurization Control Application Guide
AIRFLOW
TRACKING
OFFSET
ROOM
SUPPLY
AIRFLOW
TOTAL ROOM
EXHAUST
AIRFLOW
LAB0192R1
Figure 1. Negatively Pressurized Room Airflows.
For a negatively pressurized room, airflow tracking ensures that the total amount of air
exhausted from the room always exceeds the amount of air that is supplied to the room. This
creates a slight vacuum effect in the room, which causes air from adjacent areas to flow into
the room through the room’s leakage area.
For a positively pressurized room, airflow tracking ensures that the total amount of air
exhausted from the room is always less than the amount of air that is supplied to the room.
This creates an excess amount of air in the room, which tends to flow out from the room and
into adjacent areas.
Applying airflow tracking as the method of achieving room static pressurization does not
ensure that a specific room static pressure value is attained. However, it does ensure that the
room static pressure will be negative or positive as desired, and that the desired directional
airflow into or out of the room will be maintained. Since the goal of room pressurization is to
always ensure proper directional airflow, airflow tracking is a very reliable way of achieving
this goal.
Figure 2 shows a chemical laboratory room with an airflow arrangement that maintains a
negative static pressure. Both the room supply airflow and the total room exhaust airflow
must be controlled to be at specific values to achieve the required airflow tracking offset for
the room. The resulting deficiency in the room’s supply air creates the negative static
pressure relationship between the laboratory room and the corridors. Since the laboratory
room static pressure is negative with respect to the corridors, air always has a tendency to
flow into the laboratory from the corridors, thus preventing undesirable airflow from the
laboratory room to the corridors.
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