Chapter 5: INDOOR AIR QUALITY
Summary
This chapter considers indoor air quality and the many factors that can improve or decrease air quality in
buildings. Tighter buildings, the introduction of more and more chemicals in materials and furnishings,
and the fact that people spend more and more time indoors have served to bring public attention to indoor
air quality (IAQ) problems and solutions. Sick building syndrome is an unfortunately common result of lack
of attention to air quality. Multiple chemical sensitivity (or environmental illness) is a much less common,
but more debilitating, condition. Designing for appropriate IAQ is not an easy task—as predicting air
quality and occupant responses is difficult. Fanger has proposed a methodology and measurement units
to assist in this process.
Four major approaches to improve the quality of air within buildings exist: limiting pollutants at the source;
isolating pollutants when they are unavoidably generated; filtering air and introducing adequate fresh air;
and properly maintaining a building and its equipment. The building designer can play a role in all of
these approaches.
Indoor air pollutants can be categorized by type of contaminant (gaseous, organic, or particulate) and by
type of effect (odor, irritation, or toxicity). Odors are a simple indicator of air quality problems as people
are quite sensitive to odors. Odor sources, however, are typically difficult to isolate in many building
occupancies. Carbon dioxide concentrations are often used as an air quality indicator in spaces with
normal occupant loadings. Irritants are normally not detected by occupants, but may cause increasing
distress over time and with continuing exposure. Toxic substances, often particulates, can cause severe
health problems with continuing exposure and sufficient concentrations.
Common indoor air pollutants include odors, carbon dioxide, carbon monoxide, a wide range of
particulates, volatile organic compounds, ozone, tobacco smoke, biological contaminants, radon, and
others. Sources of such pollutants include building occupants, interior finishes and furnishings, and
building and consumer equipment and processes. The link between indoor air quality and health is
discussed in the context of green building design and chemical sensitivity.
Site planning and zoning of a building to help control indoor air quality are recommended. Ventilation,
both mechanical and passive, is a common control technique (usually mandated by codes). Exhaust of
contaminants is another common technique. Numerous strategies and examples of passive ventilation
are presented. A wide range of equipment for IAQ management is discussed, including filters, exhaust
fans, makeup air units, heat exchangers (of several types), desiccant and refrigerant dehumidifiers,
ultraviolet radiation lamps, unit air cleaners, and IAQ controls. Proper location of such equipment is
discussed.
Chapter Outline
5.1 Indoor Air Quality and Building Design
5.2 Pollutant Sources and Impacts
(a) Odors
(b) Irritants
(c) Toxic particulate substances
(d) Biological contaminants
(e) Radon and soil gases
5.3 Predicting Indoor Air Quality
(a) Ventilation rate
(b) Testing
5.4 Zoning for IAQ
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5.5 Passive and Low-Energy Approaches to Ventilation
(a) Windows
(b) Stack effect
(c) Underslab ventilation
(d) Preheating ventilation air
5.6 Equipment for Control of IAQ
(a) Exhaust fans
(b) Heating/cooling of makeup air
(c) Heat exchangers
(d) Desiccant cooling
(e) Task dehumidification and humidification
(f) Filters
(g) Locating air-cleaning equipment
(h) Ultraviolet radiation (UV)
(i) Individual space air cleansing
(j) Controls for IAQ
5.7 IAQ, Materials, and Health
(a) Multiple chemical sensitivity
(b) Materials and IAQ
(c) Green design and IAQ
References
Key Concepts
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historic concern for air quality (and resultant building systems)
trends leading to heightened concern about building air quality
sick building syndrome (as a result of poor indoor air quality)
design for indoor air quality (as a difficult task)
IAQ control strategies (limit sources, isolate sources, filter air, dilute pollutants, maintain building
and equipment)
building commissioning (as a means of ensuring Owner’s Project Requirements)
indoor air pollutants/contaminants (as design concerns)
odors (as an indicator of air quality)
carbon dioxide (as an indicator of air quality)
irritants (as a class of pollutants)
volatile organic compounds (VOCs; as a class of pollutants)
toxic substances (as a class of pollutants)
biological contaminants (as a class of pollutants)
radon (a radioactive soil gas)
outgassing (from building materials)
moisture (as a catalyst for biological contaminants)
multiple chemical sensitivity (a condition also known as environmental illness)
ventilation (as an approach to improve IAQ)
makeup air (as an approach to improve IAQ)
replacance (a measure of the effectiveness of air exchange)
site planning (as a tool for improving building IAQ)
passive approaches (as an IAQ control strategy)
stack effect (as a means of inducing air flow)
filters (particulateBpanel and media; adsorption)
air washers (as a method for improving IAQ)
electronic air cleaners (self-charging, charged media, and two-stage)
ultraviolet radiation (as a biological control means)
equipment location (as a design issue)
ASHRAE Standards 62.1 and 62.2 (as IAQ design standards)
LEED (as a green design guideline impacting IAQ design)
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Terminology and Metrics
Important Terminology
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indoor air quality (IAQ)
sick building syndrome
contaminants (gaseous, organic, particulate)
odors
carbon dioxide (CO2)
irritants (particles and gas dispersoids)
volatile organic compounds (VOCs)
tobacco smoke
asbestos
respirable particles
biological contaminants
radon
outgassing
Legionnaires’ disease
multiple chemical sensitivity
environmental illness
ventilation
replicance
Material Safety Data Sheets (MSDS)
exhaust air
makeup air
stack effect
transpired collector (unglazed)
breathable wall
economizer cycle
indirect evaporative cooling
air-to-air heat exchanger
energy recovery ventilator (ERV)
heat pipe
energy transfer wheel
sensible heat
latent heat
desiccant
dehumidification
refrigerant dehumidifier
air filter
high-efficiency particle arrestance (HEPA) filter
adsorption
activated charcoal
ultraviolet (UV) radiation
photocatalytic oxidation
germicidal
building management system (BMS)
LEED (Leadership in Energy and Environmental Design)
Important Metrics
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ACH (air changes per hour)
cfm (air flow rate, cubic feet per minute)
olf (a proposed unit of air pollution)
decipol (a proposed unit of perceived air quality)
ppm (concentration, parts per million)
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Links to Resources
U.S. Environmental Protection Agency, Research Triangle Park Campus:
http://www.epa.gov/rtp/new-bldg/index.htm
U.S. Environmental Protection Agency, Indoor Environments Division (IAQ):
http://www.epa.gov/iaq/
The New Buildings Institute (scroll to link for Commercial Building Indoor Air Quality):
http://www.newbuildings.org/mechanical.htm
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