This page provides our index to building indoor air quality investigation, testing, problem identification and remedies. We include guides to practices guide for testing or assuring good indoor air quality:

These articles also detail indoor air quality (IAQ) testing, diagnosis, and remedies including how to test & remove indoor air contaminants: gases, particles, odors, others.

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.

Our page top photo shows that even the naked eye can see comparatively large airborne particles indoors.

Article Contents

• BEST PRACTICES FOR IMPROVING INDOOR AIR IN HOMES
  • OVERVIEW OF INDOOR AIR QUALITY ISSUES
  • INDOOR AIR vs. OUTDOOR AIR CONTAMINATION
  • ACCEPTABLE RISK FOR INDOOR AIR
• HEALTH EFFECTS OF INDOOR AIR POLLUTANTS
  • SHORT-TERM HEALTH EFFECTS OF EXPOSURE TO INDOOR POLLUTANTS
  • LONG-TERM HEALTH EFFECTS OF EXPOSURE TO INDOOR POLLUTANTS
• COLLECTING DUST SAMPLES FOR IAQ ASSESSMENT

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

Here we provide detailed, unbiased 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 (Steve Bliss, J Wiley & Sons) , by Steven Bliss, courtesy of Wiley & Sons.

Our photo illustrates an indoor air particle sample dense with fiberglass, fungal hyphae, and Penicillium/Aspergillus spore chains - some are marked by red lines - indicating a nearby mold contamination source.

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

To find what you need quickly, if you don't want to scroll through this index you are welcome to use the page top or bottom SEARCH BOX to search InspectApedia for specific articles and information.

Overview of Indoor Air Quality Issues & Solutions

As noted in Best Practices Guide to Residential Construction (Steve Bliss, J Wiley & Sons) (at page bottom, Click to Show or Hide to see book information):

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, or 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. W

hile 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. EPA team 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.

Compare our airborne dust photograph at left with the similar image at page top for two examples of the extreme range of airborne particle contaminants that may be present in a building.

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.

Note: For a helpful discussion of just what constitutes "adequate ventilation",

see USE WITH ADEQUATE VENTILATION ? [PDF], ASHRAE Journal, May 2018. Offermann, Francis (Bud) J., P.E., C.I.H., ASHRAE & Mark Nicas, Ph.D., MPH, C.I.H.

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, pre-existing medical conditions, and his or her individual sensitivity to the chemical or biological compound in question.

For example, MOLD,

or POLLEN,

or INSECT FRAGMENTS,

or INSECT FECALS,

and ANIMAL ALLERGENS / PET DANDER (dander, etc.), elicit a range of allergic reactions in some, while others are unaffected.

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 REQUIREMENTS 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 HAZARDS in BUILDINGS,

or 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 BYPRODUCTS 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 GAS, 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 (Steve Bliss, J Wiley & Sons) .

Collecting & Testing Building Dust Samples for Indoor AIr Quality Assessment

Reader Question: how can I collect a dust sample for lab analysis to screen for problem particles?

Can you tell me the best procedure for getting a dust sample analyzed to see if there are indications of mold, insects, pollen, small fiberglass particles, or other indoor irritant particles? - Maurice 2/5/2010

I am looking through the site so that I can follow the suggested steps to test a dust sample from my apartment. Can you recommend a lab to send it to? Thank you. - Peggy Sissleman 6/15/2011

Reply:

Please see DUST SAMPLING PROCEDURE where we describe when, where, & how best to collect a sample of settled dust from a representative building surface.

Just about any forensic microscopy lab, including many of the labs who accept mold test samples, should be able to examine your dust to let you know what particles are dominant and whether or not the dust contains clues suggesting that further building investigation is needed.

Dust samples are also useful to track down annoying or apparently unusual quantities of indoor dust to its probable source. For example, we may examine a settled dust sample as well as a snip of carpeting fiber or a sample of building insulation to determine if that carpet or insulation is the source.

Watch out: keep in mind that while airborne particles are a key component in IAQ investigations, particle analysis will not detect irritating or hazardous gases, VOCs, odors, etc.

Reader Question: where can I mail building dust samples for analysis?

30 Oct 2014 Maria said

Where can I mail dust samples to see what they contain - Maria

Reply:

Maria

You can use any environmental test lab - to avoid any possible conflict of interest, please do not send dust samples to our own forensic lab.

For environmental or forensic investigative support and lab work, you can use any forensic lab provided you first check that their area of expertise matches your needs.

For strange particle analysis, building dust analysis, fiberglass particle screening, mold contaminant screening contact these expert forensic microscopists:

• Daniel Baxter (dbaxter@san.rr.com) or
• Larry Wayne (lew@forensica.com)
• ASBESTOS TESTING LAB LIST provides directories of certified asbestos test labs organized by country, state, or province, and city.
• CONSULTANTS & EXPERTS DIRECTORIES provides an index to directories of various experts & services.
• ENVIRONMENTAL INSPECTORS & TESTING SERVICES provides a directory organized by country, state, or province, and city.

For mold or general environmental dust samples, also contact our backup:

• Susan Flappan, 11020 W. 122nd St. Overland Park KS 66213 USA, Tel: 913 322 2237. toll free number of 866 225 MOLD Website: http://moldetect.com/ Email: sflappan@moldetect.com
• EMS lab is a very large and competent network of labs offering a wide range of services, Website: www.emlab.com

InspectAPedia.com is an independent publisher of building, environmental, and forensic inspection, diagnosis, and repair information for the public - we have no business nor financial connection with any manufacturer or service provider discussed at our website.

 

Helpful IAQ PDFs

• [1] Indoor Air Quality (IAQ) ASHRAE STANDARD [PDF] 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.
• [2] ASHRAE Fresh Air Ventilation System [PDF] 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" DF] 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."
• CRAWL SPACE MOISTURE CONTROL [PDF] U.S. Department of Energy
• ENERGY RECOVERY VENTILATION SYSTEMS for BUILDINGS [PDF] U.S. Department of Energy
• ENERGY SAVINGS METHODS: WHOLE HOUSE SYSTEMS APPROACH [PDF] U.S. Department of Energy
• JHCS, MODEL STATE INDOOR AIR QUALITY ACT [PDF] Johns Hopkins Center for Health Security 700 E. Pratt Street, Suite 900 Baltimore, MD 21202 Tel: 443-573-3304 centerhealthsecurity@jhu.edu centerforhealthsecurity.org
  Excerpt:
  
  The Model State Indoor Air Quality Act (MSIAQA) is intended to be adapted and adopted by state legislatures as a legal framework for good IAQ in public spaces, outlining best practices for how to monitor implementation, inform the public about the quality of indoor air and the benefits of good IAQ, adjust acceptable standards based on the latest research from expert bodies, and seek compliance among building owners.
• MOISTURE CONTROL in BUILDINGS [PDF] U.S. Department of Energy
• MOISTURE CONTROL in WALLS [PDF] U.S. Department of Energy
• NATURAL VENTILATION for BUILDINGS [PDF] U.S. Department of Energy
• Offermann, Francis (Bud) J., P.E., C.I.H., ASHRAE & Mark Nicas, Ph.D., MPH, C.I.H., USE WITH ADEQUATE VENTILATION ? [PDF], ASHRAE Journal, May 2018, also available as a PDF here with permission of the authors.
  Abstract:
  
  Consumer products such as paints, cleaning chemicals, and adhesives often contain toxic volatile chemicals. When these products are used indoors, these chemicals are released into the air resulting in inhalation exposures to applicators and other occupants.
  
  The resulting indoor concentrations can result in exposures that cause acute adverse health effects, including death, and/or explosion risks.
  
  Warning labels on these products and information in “safety data sheets” often simply caution to “use with adequate ventilation.”
  
  Excerpt:
  Providing consumers with the required ventilation rates and product quantity limitations for indoor applications of paints, cleaning chemicals, and adhesives should significantly reduce adverse health impacts associated with the use of these products.
• R-VALUE of Wood [PDF] U.S. Department of Energy
• SPOT VENTILATION for houses, U.S. Department of Energy
• SLAB on GRADE Foundation Moisture and Air Leakage [PDF] U.S. Department of Energy
• VAPOR BARRIERS or VAPOR DIFFUSION RETARDERS [PDF] U.S. DOE - how vapor barriers work, types of vapor diffusion barriers, installing vapor barrier
• VENTILATION for ENERGY-EFFICIENT BUILDINGS [PDF] Purpose of ventilation, ventilateion strategies, etc.
• WEATHER RESISTIVE BARRIERS [PDF] how to select and install housewrap and other types of weather resistive barriers, U.S. DOE
• WHOLE HOUSE VENTILATION SYSTEMS [PDF] U.S. Department of Energy
• WHOLE HOUSE BALANCED VENTILATION SYSTEMS [PDF] U.S. Department of Energy
• WHOLE HOUSE EXHAUST VENTILATION SYSTEMS [PDF] U.S. Department of Energy
• WHOLE HOUSE SUPPLY VENTILATION SYSTEMS [PDF] U.S. Department of Energy
• BASEMENT MOISTURE CONTROL [PDF] U.S. Department of Energy

...

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Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

Rodent feces and rats in my home were not properly cleaned-up

Rodent feces from a huge infestation were vacuumed and swept up in a home prior to learning the dangers of doing so without taking appropriate measures first.

Is a commercial type HEPA filter going to filter out any dander /bacteria/viruses they carry and mold spores that are also present or is another type filter recommended. Your prompt attention is needed and appreciated as there is someone living in the home. - On 2022-11-18 yb Joy

Reply by InspectApedia (mod) - living in the space after a heavy rodent infestation if proper remediation wasn’t done

@Joy,

It is very concerning that someone is living in the space after a heavy rodent infestation if proper remediation wasn’t done. This is especially so if building occupants are at particular risk including elderly, infants, and asthmatics. There is risk of a number of viral or bacterial illnesses for the residents.

Proper cleanup includes not only removal of rodent feces but disinfecting of all surfaces and being sure any HVAC ductwork has been inspected and addressed by a professional.

This first link gives a general overview of the necessary process to follow:

CLEANING UP AFTER RODENTS [PDF] U.S. CDC

This second one gives more specific information and steps to follow using a particular disinfectant product.

Contec®, "CLEANING & DISINFECTING GUIDELINES FOR BIRD, BAT, AND RODENT DROPPINGS " [PDF] Contec® Sporicidin® Contec, Inc. P.O. Box 530 Spartanburg, SC 29304 USA Tel: +1-864-503-8333 Toll Free US, Canada, PR: 1-800-289-5762 Email: info@contecinc.com

Cleanup projects like this are dangerous and require proper attire and safety equipment.

My OPINION is that if, in fact, there were significant levels of dangerous contaminants, the resident should vacate the premises until adequate remediation has been completed.

Please let us know if you have additional questions.

 

I think fiberglass air ducts are making me sick: what do I do?

Hi, I have been feeling itchy eyes, sore throat, dry lips, wheezing in my home. I have had people with fancy equipment come to the house and each one has said something different ( mold, no mold, change ac ducts, nothing wrong) and between it all, my health is getting worse.

I even went to a doctor to see if my head could be causing all of these symptoms because I am severely allergic, it seems to be affecting just me. I have spent several hundreds to thousands to figure out what is happening if mold or fiberglass and a solution.

I have lined fiberglass in enclosed wall ac duct so I do not have an attic. I purchased a snake camera, but didn't want to go to far and saw black garbage bag looking like lining and some small gray dust.

I paid for a non- molested cleaning of ducts where a HEPA vacuum sucked everything out. I installed the blue light and an allergen filter. I am going insane at night. I get light headed and nausea when indoors for a bit. Who can I trust to come inspect for fiberglass contamination in duct work ?

Also, the main ac unit is clean and there were yellow insulation visible in that main component area, of which I sealed with mastic tape. I am almost positive there is fiberglass in the household. Please, I do not know what else to do. - On 2021-05-22 by Yesy

Reply by inspectapedia.com.moderator (mod) - concerned about fiberglass dust

@Yesy,

From the recommended reading links above you'll want to review

https://inspectapedia.com/Fiberglass/Fiberglass_Hazards.php

FIBERGLASS HAZARDS

...

Continue reading at INDOOR AIR QUALITY IMPROVEMENT, KEY STEPS or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see INDOOR AIR QUALITY IMPROVEMENT FAQs - questions and answers posted originally on this page.

Or see these

Recommended Articles

• AIR FILTERS for HVAC SYSTEMS - home
• AIR POLLUTANTS, COMMON INDOOR
• INDOOR AIR QUALITY IMPROVEMENT GUIDE - home

Suggested citation for this web page

INDOOR AIR QUALITY IMPROVEMENT GUIDE at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

Or see this

INDEX to RELATED ARTICLES: ARTICLE INDEX to BUILDING INDOOR AIR QUALITY IAQ

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Citations & References

In addition to any citations in the article above, a full list is available on request.

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