United States Air and Energy Engineering

Environmental Protection Systems Laboratory

Agency Research Triangle Park, NC 27711

E AP Project Summary

Research and Development EPA/600/SR-95/014 February 1995

The study evaluates heating, ventilating, and air-conditioning (HVAC) systems as contaminant emission sources

that affect indoor air quality (IAQ). Various literature sources and methods for

characterizing HVAC emission sources

are reviewed. Available methods include in situ tests, longitudinal and

cross-sectional studies, and laboratory

studies. A critique of the literature reveals that few studies are well-controlled, comprehensive, and quantitative. Significant gaps in the data are

highlighted and procedures are suggested to improve the characterization

of bioaerosol and volatile organic compound (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 water systems, poor control of humidity,

poorly designed humidifying systems,

and inadequately maintained cooling

coils and drip pans. IAQ problems appear to be exacerbated by dust accumulation and by the presence of fibrous insulation. Other problems include entrainment, migration, and infiltration of indoor and outdoor contaminants that are distributed to indoor

spaces by the HVAC system. Good design and operation of HVAC systems,

including the appropriate placement

and maintenance of air intakes, building pressurization, and local exhaust

in source areas, are all important. More

HVAC Systems as Emission

Sources Affecting Indoor Air

Quality: A Critical Review

Stuart Batterman and Harriet Burge

limited data implicate dust (resulting

from inadequate filtration and maintenance of filters) as a sink and secondary source for VOCs.

This Project Summary was developed

by EPA’s Air and Energy Engineering

Research Laboratory, Research Triangle Park, NC, to announce key findings 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 airconditioning (HVAC) systems have been

considered to be a part of the solution to

indoor air quality (IAQ) problems. The provision of clean outdoor air to the occupied

spaces by the HVAC system can remove

airborne contaminants and dilute occupant-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-Conditioning Engineers jointly funded a research

project with the University of Michigan to

identify and quantify sources of indoor air

pollution from HVAC systems in nonindustrial buildings.

Sources were identified through the process of a literature review. Sources were

quantified in various buildings on the Uni-
2

• •

United States

Environmental Protection Agency

Center for Environmental Research Information

Cincinnati, OH 45268

EPA/600/SR-95/014

Official Business

Penalty for Private Use $300

BULK RATE

POSTAGE & FEES PAID

EPA

PERMIT No. G-35

versity of Michigan campus. The report

cites only the findings of the critical literature review.

Approach/Findings

The review focuses on contaminant

sources and highlights sources and problems in HVAC systems. The literature reviewed included data and reviews in peerreviewed 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 exacerbated by dust accumulation and infiltration of outdoor air contaminants that are

distributed to occupied spaces by the

HVAC system.

A number of studies describe the importance of good fundamental HVAC system 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 systems 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 contributions from major HVAC components.

Stuart Batterman is with the University of Michigan, Ann Arbor, MI 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