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Indoor Air Quality Improvement Guide
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Indoor Air Quality Testing, Diagnosis, and Remedies
Removing or keeping out indoor contaminants
How clean does indoor air need to be for a healthy and comfortable environment?
What are the health effects of indoor air pollutants?
Home ventilation strategies
Best methods for cleaning & filtering indoor air
Questions & answers about indoor air quality, contaminants, testing, ventilation designs, etc.

These indoor air quality and health articles discuss in detail the steps needed to test, diagnose and improve indoor air quality in homes and commercial buildings. Examples of topics we cover include air filters, allergens indoors, carpeting, Chinese drywall, house dust, unsafe gases found indoors, mold in buildings, odors, and building ventilation.

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Indoor Air Quality - Best Practices for Improving Indoor Air in Homes

We provide detailed, un-biased advice on finding and correcting indoor air quality problems as well as advice on new construction details for a combination of low building energy cost and high indoor air quality. This article series 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

Overview of Indoor Air Quality Issues & Solutions

As noted in Best Practices Guide to Residential Construction:

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.

For example, mold, pollen, insect fragments, insect fecals, and animal protein (dander, etc.), elicit a range of allergic reactions in some, while others are unaffected. [See ANIMAL ALLERGENS / PET DANDER]

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.

See COMBUSTION AIR for additional details about the requirement for combustion air. COMBUSTION AIR for TIGHT buildings explains how to provide outside combustion air for tight buildings. See COMBUSTION GASES & PARTICLE HAZARDS for an explanation of the dangers of inadequate combustion air. See COMBUSTION PRODUCTS & IAQ for the relationship between fuel burning appliances and building indoor air quality. More about carbon monoxide - CO - is at CARBON MONOXIDE - CO and at CARBON MONOXIDE WARNING.

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.

-- Adapted with permission from Best Practices Guide to Residential Construction.

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Technical Reviewers & References

InspectAPedia.com^® - Daniel Friedman - Publisher & Editor.
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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ENVIRONMENTAL HAZARDS - INSPECT, TEST, REMEDY

INDOOR AIR QUALITY IMPROVEMENT GUIDE

"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.
"ASHRAE Fresh Air Ventilation System", Jie Chen et als, describes a fresh air ventilation system designed to meet ASHRAE 62.2P Standard.
"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, Ventilating 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."
"Energy Efficient Lab Design", Nicolas Lemire, Eng., Member ASHRAE, and Roland Charneux, Eng., Fellow ASHRAE, American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. (www.ashrae.org). Reprinted by permission
from ASHRAE Journal, (Vol. 47, No. 5, May 2005). ©ASHRAE

Guide to Asbestos Exposure Hazards Indoors

According to Best Practices Guide to Residential Construction and other expert sources as well:

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 IDENTIFICATION IN buildings for extensive details about how to recognize asbestos in buildings by visual inspection, what building products used asbestos, and asbestos advice

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Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
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 Amazon.com and also Wiley.com. See our book review of this publication.
Decks and Porches, the JLC Guide to, Best Practices for Outdoor Spaces, Steve Bliss (Editor), The Journal of Light Construction, Williston VT, 2010 ISBN 10: 1-928580-42-4, ISBN 13: 978-1-928580-42-3, available from Amazon.com
Basement Moisture Control, U.S. Department of Energy
Building Pathology, Deterioration, Diagnostics, and Intervention, Samuel Y. Harris, P.E., AIA, Esq., ISBN 0-471-33172-4, John Wiley & Sons, 2001 [General building science-DF] ISBN-10: 0471331724 ISBN-13: 978-0471331728
Building Pathology: Principles and Practice, David Watt, Wiley-Blackwell; 2 edition (March 7, 2008) ISBN-10: 1405161035 ISBN-13: 978-1405161039
Historic Preservation Technology: A Primer, Robert A. Young, Wiley (March 21, 2008) ISBN-10: 0471788368 ISBN-13: 978-0471788362
Building Pathology, Deterioration, Diagnostics, and Intervention, Samuel Y. Harris, P.E., AIA, Esq., ISBN 0-471-33172-4, John Wiley & Sons, 2001 [General building science-DF] ISBN-10: 0471331724 ISBN-13: 978-0471331728
Crawl Space Moisture Control, U.S. Department of Energy
Energy Recover Ventilation Systems for buildings, U.S. Department of Energy
Energy Savings Methods: Whole House Systems Approach, U.S. Department of Energy
Historic Preservation Technology: A Primer, Robert A. Young, Wiley (March 21, 2008) ISBN-10: 0471788368 ISBN-13: 978-0471788362
Log Homes: Minimizing Air Leakage in Log Homes, U.S. Department of Energy
Log Homes: Controlling Moisture in Log Homes, U.S. Department of Energy
Log Homes: Log Home Design, U.S. Department of Energy
Moisture Control in buildings, U.S. Department of Energy
Moisture Control in Walls, U.S. Department of Energy
Quality Standards for the Professional Remodeling Industry, National Association of Home Builders Remodelers Council, NAHB Research Foundation, 1987.
Quality Standards for the Professional Remodeler, N.U. Ahmed, # Home Builder Pr (February 1991), ISBN-10: 0867183594, ISBN-13: 978-0867183597
Natural Ventilation for buildings, U.S. Department of Energy
R-Value of Wood, U.S. Department of Energy
Spot Ventilation for houses, U.S. Department of Energy
Slab on Grade Foundation Moisture and Air Leakage, U.S. Department of Energy
Straw Bale Home Design, U.S. Department of Energy
"Vapor Barriers or Vapor Diffusion Retarders", U.S. DOE: how vapor barriers work, types of vapor diffusion barriers, installing vapor barrier
Ventilation for energy efficient buildings, Purpose, Strategies, etc.,
Weather-Resistive Barriers, how to select and install housewrap and other types of weather resistive barriers, U.S. DOE
Whole House Ventilation Systems, U.S. Department of Energy
Whole-House Balanced Ventilation Systems, U.S. Department of Energy
Whole-House Exhaust Ventilation Systems, U.S. Department of Energy
Whole-House Supply Ventilation Systems, U.S. Department of Energy
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Indoor Air Quality - Best Practices for Improving Indoor Air in Homes

Overview of Indoor Air Quality Issues & Solutions

Indoor Air is Typically More Contaminated than Outdoor Air

Acceptable Risk: Just How Clean Does Indoor Air Need to Be?

Health Effects of Indoor Air Pollutants

Short-Term Health Effects of Exposure to Indoor Pollutants

Long-Term Health Effects of Exposure to Indoor Pollutants

Questions & Answers regarding this article

Ask a Question or Search InspectAPedia

Technical Reviewers & References

Guide to Asbestos Exposure Hazards Indoors

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

Indoor Air Quality Improvement Guide
InspectAPedia^® -