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Here we discuss steps to improve indoor air quality in homes. This article includes excerpts or adaptations from Best Practices Guide to Residential Construction, by Steven Bliss, courtesy of Wiley & Sons.
Our page top photo shows that even the naked eye can see comparatively large airborne particles indoors. But many indoor contaminants are simply too small to see, or are not particles at all but rather gases or chemicals. See ENVIRONMENTAL HAZARDS - INSPECT, TEST, REMEDY for our full list of environmental hazard identification and remedy related to buildings
Two trends have conspired to place significant stresses on
the indoor environment over the past two decades. First,
houses are being built much tighter today than they were a
generation ago, either deliberately by energy-minded
builders or simply as a by-product of using modern building
materials, such as plywood, drywall, insulation, and tight-
fitting doors and windows. Second, the number of synthetic
building materials has rapidly expanded to include synthetic
carpeting, a wide variety of plastics, wood composites,
adhesives, sealants, and finishes.
These, along with the wide
variety of cleaning, personal care, and hobby products stored
and used indoors provide most homes with an ample source
of airborne chemicals, many of which have not been well
studied, either alone or in combination with others. Some
leading indoor-air-quality advocates have referred to this
unknown mix of airborne compounds as “chemical soup.”
Individuals with allergies, asthma, or strong chemical
sensitivities were, like the proverbial canary in the coal
mine, the first to call attention to the higher concentrations
of chemicals that were building up in our new, tighter
homes. While scientists had thoroughly studied the outdoor
air in cities and indoor air in occupational settings,
little was known about air quality in homes.
Indoor Air is Typically More Contaminated than Outdoor Air
A growing body of scientific evidence
has demonstrated that the air inside homes is typically
more polluted than outdoor air, even in polluted urban areas. For example, the U.S. EPATEAM study of over
600 residents in seven cities in the 1980s found that exposure
to toxic chemicals was much greater at home or at work
than outdoors.
Levels of about a dozen common organic
pollutants were found to be two to five times higher inside
homes than outside, regardless of whether homes were in
rural or industrial areas. And since the average person
spends far more time indoors than outside, the study concluded
that health risks from the indoor environment pose a
greater risk to most people than outdoor air pollution.
Fortunately, as builders, designers, and homeowners,
we potentially have much greater control over our indoor
environment than out of doors. Public health professionals
and researchers both in the private sector and in state and
federal agencies have identified the most significant
threats posed by indoor air pollution, as well as a number
of straightforward strategies that enable us to minimize or
eliminate the health risks.
See INDOOR AIR QUALITY & HOUSE TIGHTNESS for a discussion of the relationship between air-tightness of a home and indoor air quality and for a description of the causes of variation in indoor air quality among similarly-constructed homes.
Acceptable Risk: Just How Clean Does Indoor Air Need to Be?
Remember, there is no environment—
indoor or outdoor—that is 100% free of hazardous materials,
many of which (like radon, asbestos, and airborne particulates)
occur naturally in the environment. And while
many of these substances have been studied extensively in
the workplace, the effects of long-term exposure to the
lower levels found in most homes are not well understood.
For some indoor air pollutants, like radon, scientists have a fairly
precise understanding of the health effects and recognize
that that no exposure level is safe. However, the cost of
reducing the indoor radon level to zero (below outdoor levels) would be prohibitive for most people, so homeowners,
health professionals, and regulatory agencies do their
best to find a “cost-effective” goal that balances costs
against perceived health risks.
In the absence of clear indoor air guidelines, and taking
into account that all building projects have budget
limitations, the goal of this chapter is to identify reasonable
steps that builders and designers, and, in some cases,
homeowners can take to produce a healthy indoor environment
by eliminating or substantially reducing known hazards.
The emphasis will be on getting the greatest benefit
for the least cost, starting with the most significant hazards.
How much an individual invests in clean indoor
air is a matter of personal choice. Fortunately, with good
planning, a great deal can be accomplished for a modest
investment.
For individuals with special sensitivities to chemicals,
dust, or biological materials such as indoor mold contamination, the measures described here
may not be adequate. A more comprehensive approach
under the guidance of environmental health specialists is
advisable.
Health Effects of Indoor Air Pollutants
Indoor air pollutants at high levels can cause acute illness,
while lower levels may lead to health problems only after
years of exposure. In the case of certain carcinogens, such
as radon, health professionals believe that a single exposure
could lead to health problems many years later (although
the greater the total exposure over time, the greater
the risk).
While the effects of some pollutants are well understood,
for others further research is needed to determine
what concentrations and types of exposure will impair
health. Also, it is important to bear in mind that different
people react very differently to indoor pollutants.
Even in the absence of definitive studies on every pollutant,
there is little disagreement that reducing exposure
to volatile organic compounds, combustion gases, radon,
common allergens, and other indoor pollutants is a worthwhile
goal for all homeowners and particularly vital for
the very young or for those with allergies or respiratory
problems. [See MOLD RELATED ILLNESS for an extensive list of occupant-reported illnesses related to mold and other indoor contaminants.]
Short-Term Health Effects of Exposure to Indoor Pollutants
High levels of indoor pollutants
can cause immediate symptoms after one or more
exposures. The symptoms may look like those of a cold or
virus, including irritation of the eyes, nose, and throat,
headaches, dizziness, and fatigue. These effects are usually
short-term and reverse quickly once the person leaves
the building or the pollutant is identified and eliminated.
Short-term exposures can also trigger asthma episodes and
lead to other serious allergic responses, including hypersensitivity
pneumonitis and humidifier fever, both of
which may first appear as flu-like symptoms.
For many pollutants, the exposure level at which
symptoms first appear is highly variable. Key factors
include a person’s age, preexisting medical conditions, and
his or her individual sensitivity to the chemical or biological
compound in question.
Also, the
level at which formaldehyde elicits symptoms ranges from
as little as .04 ppm to as much as 5.0 ppm (parts per
million), depending on an individual’s sensitivity. To complicate
matters, people can develop sensitivities to both
biological and chemical pollutants at any point in their
lives, possibly from repeated exposures to low levels of
the substance.
Long-Term Health Effects of Exposure to Indoor Pollutants.
Some of the most toxic
substances in our homes, such as lead, asbestos, and radon,
can under some circumstances cause long-term irreversible
damage to health. Many types of air pollutants increase the
frequency and severity of asthma attacks.
Combustion
by-products have been linked to reduced lung function in
developing children. Some health problems, including certain
cancers, have long latency periods and may show up
years after exposure to a pollutant such as tobacco smoke
or radon.
There is also ample evidence that some materials,
such as formaldehyde, are “sensitizers,” which can
cause a person to become hypersensitive after years of
low-level exposure. Whether indoor air quality contributes
to other chronic health problems, such as heart disease,
respiratory diseases, and cancers (other than lung cancer
from radon and secondhand smoke), is unclear; but there
is evidence that all major internal systems can be strained
and become symptomatic as a result of poor indoor air
quality.
Steven Bliss served as editorial director and co-publisher of The Journal of Light Construction for 16 years and previously as building technology editor for Progressive Builder and Solar Age magazines. He worked in the building trades as a carpenter and design/build contractor for more than ten years and holds a masters degree from the Harvard Graduate School of Education.
Excerpts from his recent book, Best Practices Guide to Residential Construction, Wiley (November 18, 2005) ISBN-10: 0471648361, ISBN-13: 978-0471648369, appear throughout this website, with permission and courtesy of Wiley & Sons. Best Practices Guide is available from the publisher, J. Wiley & Sons, and also at Amazon.com.
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"Indoor Air Quality (IAQ) ASHRAE Standard", Ranish Joshi, Arctic India Sales, reviews the basics of IAQ, emphasizes the importance of both source control and removal of contaminants when improving indoor air quality, warns about bringing inside contaminants from outdoors, and reviews the pertinent ASHRAE IAQ standards for buildings.
"Updated ASHRAE 90.1 Energy Code May Help
Maximize The Benefits Of Energy Efficient
Technologies", Lindsay Audin, Building Operating Management, May 2005, discusses ASHRAE Standard ASHRAE 90.1-2004, the latest version of ASHRAE's energy code, encompassing updates to the ASHRAE 90.1-2001 standard. "Written to allow easy incorporation into specifications for new buildings and renovations, 90.1-2004 lays
out minimum requirements for a building’s envelope, electrical power systems and equipment, lighting,
heating, Ventilationg and air conditioning, service, water heating, and energy management.
Under the 1992 federal Energy Policy Act (EPAct), ASHRAE 90.1 was mandated as the basis for all
state building codes as they affect energy use, starting with ASHRAE 90.1-1989. Under EPAct, the 1999
version became law in July 2004, but has yet to be adopted by all states. Since the 1999 version was
somewhat dated by the time it became a requirement, some states, especially those having high energy
prices, have already updated their building codes to the 2001 version. Some states and cities, such as
Phoenix, are now going further by leapfrogging the 2001 edition and enacting part or all of the 2004
edition instead."
Asbestos is found in buildings mainly in older homes in pipe and boiler
insulation, asbestos shingles, textured paint, and floor tiles.
It becomes a health hazard only if it is disturbed by cutting,
sanding, or other remodeling activities. Loose, “friable”
pipe insulation is a problem since it can be easily damaged
and may spread fibers into the air.
Health Effects of Exposure to Asbestos. The most dangerous asbestos fibers are
too small to see. If inhaled, they can penetrate deep into
the lungs and accumulate there. Asbestos can cause lung
cancer, mesothelioma (cancer of the chest and abdominal
linings), and asbestosis (irreversible lung scarring). Most
people with asbestos-related diseases were exposed to
high levels on the job or were exposed to asbestos fibers
brought home on the clothes and equipment of workers.
Reducing Exposure to Asbestos in Buildings. Undamaged asbestos is best left
alone. If asbestos materials are more than slightly damaged,
or if they need to be altered or removed due to a
remodeling project or equipment replacement, hire a state-
licensed asbestos-abatement professional to evaluate and
then encapsulate or remove the asbestos.
See ASBESTOS in BUILDINGS for extensive details about how to recognize asbestos in buildings by visual inspection, what building products used asbestos, and asbestos advice
...
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
Our recommended books about building design, inspection, and repair, and about indoor environment testing, diagnosis, and cleanup are at the InspectAPedia Bookstore.
Best Practices Guide to Residential Construction, by Steven Bliss. John Wiley & Sons, 2006. ISBN-10: 0471648361, ISBN-13: 978-0471648369, Hardcover: 320 pages, available from Wiley.com and also at Amazon.com. See our book review of this publication.
More Information on Building Diagnostic Inspections and Repairs
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The Mold Information Center: What to Do About Mold in Buildings, When and How to Inspect for Mold, Clean Up Mold, or Avoid Mold Problems
Environmental Inspection, Testing, & Diagnosis On-Site IAQ, Gas, Air Testing, Mold Investigation, Sick Building Diagnosis, Lab Services, & Remediation Plan Preparation - indoor air quality testing, problem source determination, supporting lab work, written remediation plan addressing removal of environmental and other hazards and prevention of their recurrence.
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