Appendix C 415
circulation of air spreads pollutants emitted from localized sources
throughout a building so that a larger population is exposed; however,
recirculation may decrease the pollutant concentration near the source.
Also, recirculation of air through air cleaning systems can reduce indoor
pollutant concentrations.
The pattern of airflow within rooms also influences indoor pollut-
ant exposures. A floor-to-ceiling indoor airflow pattern, called displace-
ment ventilation, can reduce pollutant concentrations in the breathing
zone. A short-circuiting air flow pattern between supply and return air
grills at ceiling level can increase pollutant concentrations in the breath-
ing zone.
4.5.7 Maintenance, Cleaning, and Commissioning
Maintenance, cleaning, and commissioning of the HVAC system
and building are generally thought to be significant determinants of
indoor pollutant concentrations. Poor HVAC system maintenance may
lead to poor control of indoor thermal comfort or outside air supply
and to growth of microorganisms inside the HVAC system. Air filters
may become sources of odors or a substrate for microbiological growth
(e.g., Elixmann et al. 1990, Martikainen et al. 1990). HVAC system com-
missioning and air balancing help to assure that the system performs
as intended. In a large study of office buildings with health complaints
(Sieber et al. 1996), significantly increased prevalences of respiratory
health symptoms were associated with poorer HVAC maintenance and
less frequent building cleaning.
The methods and quality of building cleaning affects odor emis-
sions from surfaces and the quantity of particles on surfaces that may
become suspended in the air.
While increased maintenance and cleaning is generally considered
beneficial, maintenance activities and products can be sources of indoor
pollutants (e.g., cleaning compounds, waxes) and cleaning activities can
be a source of resuspended particles.
4.6 ACUTE NON-SPECIFIC HEALTH
SYMPTOMS AND BUILDING RELATED ILLNESS
The general public is familiar with many of the health effects that
may be influenced by IEQ (and by energy conservation measures),
such as acute respiratory diseases, allergies, asthma, and cancer. This
document will not discuss the nature of these health effects. Rather, this