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The Big Picture of Indoor Air Quality – Excerpt

  • 1.  The Big Picture of Indoor Air Quality – Excerpt

    Posted 04-29-2022 12:09

    The quote below is a classic from the 1893 book, Ventilation and Heating, by John Shaw Billings.  The imagery of wearing someone else's dirty underwear may shock you, but Billings makes a compelling point.  We essentially do something worse whenever we take a breath indoors.

    Most civilized men and women are unwilling to put on underclothing that has just been taken off by another person or to put into their mouths articles of food or drink that have recently been in other people's mouths but they take without hesitation into their lungs air that has just come from other people's mouths and lungs or from close contact with their soiled clothing or bodies.

    ~ John Shaw Billings

    It's not just air recently expelled from other people's lungs we should worry about, though.  Indoor air is often more polluted than outdoor air.  It's a soup of particulate matter of various sizes, volatile organic compounds, skin flakes, dust mite carcasses, mold spores, and more.  And we suck all that nasty stuff into our lungs with every breath.

    The average American spends 87% of their time indoors, making the quality of their indoor air really important.   So, let's look at the big picture of indoor air quality today.  We'll start with the bad stuff in a home's air and where it comes from, then highlight the three best ways to ensure good IAQ, and finish with a step that is just now coming into its own for homes:  monitoring indoor air quality.

    What's in your air?

    Often when you look up indoor air pollutants, you find lists like this:

    1. Carbon monoxide (CO)
    2. Radon
    3. Ozone (O3)
    4. Volatile organic compounds, or VOCs
    5. Nitrogen dioxide (NO2)
    6. Secondhand smoke from cigarettes (SHS)
    7. Bioeffluents (including carbon dioxide)
    8. Particulate matter
    9. Asbestos
    10. Viruses and bacteria
    11. Mold
    12. Allergens

    In fact, that list is a rearranged version of the list in my article about which indoor pollutants matter most.  But let me break it down further.  That list contains two different types of airborne pollutants:  Particles and gases.  The first five pollutants in the list are gases.  Numbers 6 and 7 are mixtures of particles and gases.  The last four are particles.  It's good to think of them separately because  we deal with them in different ways, as you'll see below.

    With particulate matter, the type of particle matters.  Asbestos can do great damage in the lungs.  Viruses and bacteria can spread disease just by getting into the upper respiratory system.  Mold and allergens cause reactions in people susceptible to those pollutants.

    But sometimes it's just the size that matters.  Particles that float around in the air might otherwise would cause no ill effects.  But if they're small enough, they can increase breathing problems, aggravate asthma, and reduce lung function.  The really small ones can even get into the bloodstream, where they can lead to irregular heartbeat, nonfatal heart attacks, and premature death for people who already have heart or lung problems.

    The scale of particulate matter [credit:  US Environmental Protection Agency]
    The diagram above, from the US EPA's page on particulate matter, shows the scale of particulate matter compared to human hair and grains of sand.  Anything that's 10 microns (PM10) or smaller can lead to health problems.  The smaller particles that are 2.5 microns and smaller are a bigger risk factor.

    What you're reading here is an excerpt of my full article at Green Building Advisor.

    The sections you can't see here are available at Green Building Advisor, and they are:

    • Where do the pollutants come from?
    • Three ways to ensure good IAQ
    • Monitoring a home's IAQ
    • The big picture of IAQ

    Green Building Advisor is running a series on indoor air quality from now through June, and the full version of this article is the kickoff piece for the series.  

    Of course, you can become a GBA Prime member and have access to all their stuff.  In addition to lots of great articles, they have an extensive library of details. Their details library includes vented or unvented cathedral ceilings, roof/wall connections for various wall and ceiling types, foundation water management, and more.  If you're a builder or remodeler-whether you're doing it for yourself or others-this collection may well justify the cost of the GBA Prime membership.  Also, Martin Holladay still writes his excellent column, Musings of an Energy Nerd, twice a month.

    Or you could join just for the articles in the IAQ series and then cancel later.  Other people who will be writing articles for it are Kristof Irwin, Jon Harrod, Shelly Miller, PhD, Monica Rokicki-Guajardo, Nikki Krueger, John Semmelhack, and Cramer Silkworth.  If you've been wanting to learn more about indoor air quality, this is a great way to do it.

    Allison Bailes
    Energy Vanguard, LLC - BPI Test Center
    Decatur GA