Basic Documentation

Room Pressurization Control Application Guide
In still (non-moving) air the total pressure equals the static pressure. The total pressure in a
moving air stream is always greater than its static pressure. If the static pressure value of a
moving air stream is subtracted from the total pressure value, the resulting difference is
called the velocity pressure. This velocity pressure component bears a relationship to the
speed or velocity of the moving air stream. Thus, its value provides a means to determine the
velocity of a moving air stream.
Figure 18 illustrates the relationship of total pressure, static pressure, and velocity pressure
in a moving air stream.
AIRFLOW IN DUCT
TOTAL
PRESSURE
MEASUREMENT
STATIC
PRESSURE
MEASUREMENT
-
PRESSURE VALUE GRAPH
VELOCITY
PRESSURE
LAB0191R1
Figure 18. Moving Air Stream Pressure Relationships.
46 Siemens Building Technologies, Inc.