Air Change Effectiveness Measurements in Two Modern Office Buildings.
Air Change Effectiveness Measurements in Two Modern
Persily, A. K.; Dols, W. S.; Nabinger, S. J.
Indoor Air, Vol. 4, 40-55, 1994.
office buildings; air change effectiveness; building
performance; commercial buildings; indoor air quality;
mechanical ventilation; tracer gas; ventilation;
Local age of air and air change effectiveness were
determined in two office buildings using tracer gas
techniques to study the applicability of the associated
measurement procedures in mechanically ventilated office
buildings. Measurement issues examined include the
establishment of a uniform tracer gas concentration at
the start of the test and the relationship of
ventilation system configuration and system operation to
the test procedure. Air change effectiveness was
determined at locations in the occupied space based on
the local age of air at that location and the age of air
in the corresponding ventilation system return duct.
Values of the air change effectiveness in the occupied
space were generally close to one, which is consistent
with good mixing of the ventilation air within the
occupied space. Deviations from 1.0, on the order of
10%, did occur, but given the limited experience with
these measurement procedures in the field it is not
clear whether these deviations are significant. These
tests provide data on air change effectiveness to
supplement the limited database on mechanically
ventilated office buildings in the U.S. In addition,
the experience obtained with the measurement procedures
will assist in the development of a standardized
approach to measuring air change effectiveness in the