United States
Environmental Protection
Agency
Air and Energy Engineering
Systems Laboratory
Research Triangle Park, NC 27711
Research and Development
EPA/600/SR-95/014
February 1995
EPA Project Summary
HVAC Systems as Emission
Sources Affecting Indoor Air
Quality: A Critical Review
Stuart Batterman and Harriet Burge
The study evaluates heating, venti-
lating, and air-conditioning (HVAC) sys-
tems as contaminant emission sources
that affect indoor air quality (IAQ). Vari-
ous literature sources and methods for
characterizing HVAC emission sources
are reviewed. Available methods in-
clude in situ tests, longitudinal and
cross-sectional studies, and laboratory
studies. A critique of the literature re-
veals that few studies are well-con-
trolled, comprehensive, and quantita-
tive. Significant gaps in the data are
highlighted and procedures are sug-
gested to improve the characterization
of bioaerosol and volatile organic com-
pound (VOC) emission sources. Based
on the available literature, several HVAC
components are cited fairly frequently
as emission sources, and there is broad
agreement regarding their significance.
The components include biological
growth and bioaerosol generation in
the presence of moisture provided by
air washers and other recirculating wa-
ter systems, poor control of humidity,
poorly designed humidifying systems,
and inadequately maintained cooling
coils and drip pans. IAQ problems ap-
pear to be exacerbated by dust accu-
mulation and by the presence of fi-
brous insulation. Other problems in-
clude entrainment, migration, and infil-
tration of indoor and outdoor contami-
nants that are distributed to indoor
spaces by the HVAC system. Good de-
sign and operation of HVAC systems,
including the appropriate placement
and maintenance of air intakes, build-
ing pressurization, and local exhaust
in source areas, are all important. More
limited data implicate dust (resulting
from inadequate filtration and mainte-
nance of filters) as a sink and second-
ary source for VOCs.
This Project Summary was developed
by EPA's Air and Energy Engineering
Research Laboratory, Research Tri-
angle Park, NC, to announce key find-
ings of the research project that is fully
documented in a separate report of the
same title (see Project Report ordering
information back).
Purpose
Traditionally, heating, ventilating, and air-
conditioning (HVAC) systems have been
considered to be a part of the solution to
indoor air quality (IAQ) problems. The pro-
vision of clean outdoor air to the occupied
spaces by the HVAC system can remove
airborne contaminants and dilute occu-
pant-generated odors.
Recent studies indicate that the HVAC
system itself can act as the source of
indoor pollution in nonindustrial spaces.
This literature review was undertaken to
identify and evaluate HVAC systems as
emission sources that affect IAQ.
General Description
The U.S. Environmental Protection
Agency (EPA) and the American Society
of Heating, Refrigerating and Air-Condi-
tioning Engineers jointly funded a research
project with the University of Michigan to
identify and quantify sources of indoor air
pollution from HVAC systems in nonin-
dustrial buildings.
Sources were identified through the pro-
cess of a literature review. Sources were
quantified in various buildings on the Uni-
-------
versity of Michigan campus. The report
cites only the findings of the critical litera-
ture review.
Approach/Findings
The review focuses on contaminant
sources and highlights sources and prob-
lems in HVAC systems. The literature re-
viewed included data and reviews in peer-
reviewed journals, books and proceedings.
Based on the available literature, many
HVAC components can act as direct or
indirect sources of particles and/or volatile
organic chemicals. These can affect IAQ
under some conditions. Most prominent is
the occurrence of biological growth and
bioaerosol generation in the presence of
moisture provided by air washers and other
recirculating water systems.
These problems appear to be exacer-
bated by dust accumulation and infiltra-
tion of outdoor air contaminants that are
distributed to occupied spaces by the
HVAC system.
A number of studies describe the im-
portance of good fundamental HVAC sys-
tem design and operation, including the
appropriate placement and maintenance
of air intakes, building pressurization, and
local exhaust in source areas.
Many sources and problems related to
indoor air contaminants and HVAC sys-
tems have been identified as having the
potential to critically affect IAQ. No single
study (or collection of studies) of HVAC
emission sources was comprehensive and
examined and isolated pollutant contribu-
tions from major HVAC components.
Stuart Batterman is with the University of Michigan, Ann Arbor, Ml 48109; and
Harriet Burge is with Harvard University, Boston, MA 02115.
Russell N. Kulp is the EPA Project Officer (see below).
The complete report, entitled "HVAC Systems as Emission Sources Affecting
Indoor Air Quality: A Critical Review," (Order No. PB95-178596; Cost: $19.50,
subject to change) will be available only from
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at
Air and Energy Engineering Research Laboratory
U. S. Environmental Protection Agency
Research Triangle Park, NC 27711
United States
Environmental Protection Agency
Center for Environmental Research Information
Cincinnati, OH 45268
Official Business
Penalty for Private Use $300
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT No. G-35
EPA/600/SR-95/014
------- |