Indoor Air Quality – How I Made the Air I Breathe Healthier By Using NASA Research

Some of you may be wondering why I said in my first post that I’d rather have house plants than an air purifier.  I chose house plants because they do not use any energy other than sunlight, and because my research did not convince me that air purifiers were significantly better than houseplants.  Thus, I preferred the cheaper, more natural option.

What I said in the previous post:

To me, [naturopathic self-healing] means utilizing evidence-based natural solutions when possible, such as using house plants to improve the quality of the air in my house, rather than buying an air purifier.

The Spousal Unit and I had talked for years about getting an air purifier.  We thought that putting an air purifier in the bedroom would help us get better sleep.  I had read blogs and websites written by asthmatics and allergy sufferers who highly recommended air purifiers with HEPA filters, and they were pretty persuasive.  The only thing holding me back was the price – $500+ for a one-room HEPA filter air purifier.

“Maybe I could start with something less expensive,” I thought.  “What about those Himalayan salt lamps?”  According to the advertisements, a Himalayan salt lamp “works as an air purifier by emitting negative ions into the air.”  And they retail for $25-$30 for a smaller lamp.  So I did some research.  Unfortunately, I found that Himalayan salt lamps do not emit negative ions in a large enough quantity to have an actual effect on your indoor environment.  For a thorough examination of Himalayan salt lamps, I recommend this post over at A Breath of Reason blog.  Bottom line: they don’t improve air quality.

Ok, what about beeswax candles?  They are also touted as being good for air quality because they release negative ions.  Nope, Skepticcystic over at A Breath of Reason debunked beeswax candles too.  (See this post.)  According to her research, not only do beeswax candles not release stable negative ions, but there is no scientific evidence that beeswax is healthier to burn than other types of wax.  So, although some would argue that you should avoid the phthalates in artificially scented candles, the type of wax  a candle is made of doesn’t appear to make a difference to indoor air quality.  Bottom line: Regardless of what they are made of, burning candles does not improve indoor air quality.

So back to air purifying machines…

For a practical overview of air purifiers, check out this article from ConsumerReports.  For example, ConsumerReports suggests:

“Before you buy an air purifier, try some simple, common-sense steps to reduce indoor air pollution. Begin by vacuuming often, banning smoking indoors, minimizing use of candles and wood fires, and using exhaust fans in kitchen, bath, and laundry areas.”

As the article continues, various claims made by air purifier companies are tested.  ConsumerReports cautions that ozone-producing air purifiers are actually harmful to your health and should be avoided, particularly if you have allergies or breathing problems.  This is confirmed by the American Academy of Asthma Allergy & Immunology:

There is no debate about the negative effect of ozone…with the FDA concluding there is no place for ozone in medical treatment.” (See article here.)

For more information on the pros and cons of air purifiers, read this article from the New York Times, in which Steven Kurutz, an allergy sufferer, tested six popular air purifiers.  Here are a few excerpts from his article:

“For all their high-tech wizardry (some claim to be able to eliminate particles 0.3 microns in size and smaller), air purifiers occupy the same category as faith-based wellness products like nutritional supplements.”


“Over the years, the Federal Trade Commission has taken action against several makers of air purifiers, including brands like Honeywell and Oreck, for unsubstantiated allergy-relief claims or for advertising that their devices removed virtually all impurities from the indoor air people breathed.”

According to ConsumerReports’ deputy home editor, Celia Kuperszmid Lehrman, whom Kurutz interviewed for the article,

“The first thing you need to know about an air purifier is that most people don’t need one.”

However, some doctors do recommend air purifiers for their patients, particularly children who suffer from asthma.  So, if you have asthma or allergies (or both), talk to your doctor about whether an air purifier would be beneficial for you.

According to the American Academy of Allergy Asthma & Immunology:

There is no definite evidence of filtration clinically benefiting patients with allergic disease, but this may be the result of the studies being of insufficient durations to prove benefit.   The best review of the topic is by Sublett et al in 2010, a report of the Indoor Allergen Committee of the American Academy of Allergy Asthma and Immunology.” (See AAAAI article here.)

The Bottom Line for Air Purifiers: The different things you may be allergic to (dog allergens, cat allergens, mite allergens, mold, pollen, etc.) have different-sized particles.  You will see the most benefit if you select an air purifier that is designed to filter the particle size of the allergen that most affects you.

Conclusion from the Sublett et al report:

“As far as optimal choice of cleaning devices, initial cost and ease of regular maintenance should be considered. Portable room air cleaners with HEPA filters, especially those that filter the breathing zone during sleep, appear to be beneficial.

For the millions of households with forced air HVAC systems, regular maintenance schedules and the use of high-efficiency disposable filters appear to be the best choices.

However, further studies and research in this area are desirable to make more definitive recommendations in the role of air filtration on improving disease outcomes.”

Ok, so I could buy an expensive HEPA filter air purifier for my bedroom, which might help us sleep a bit better.  Are there any other options?

That’s when I remembered that house plants help improve indoor air quality.

Most of us learned in school that plants breathe in carbon dioxide and breathe out oxygen (roughly speaking), which is great for humans because we breathe in oxygen and breathe out carbon dioxide.  So having plants in the house helps increase the oxygen level in the air and decrease the carbon dioxide level.  But indoor plants can do more than just produce oxygen.

NASA published research in 1989 which demonstrated that house plants help reduce indoor air pollution.  Due to the energy crunch in the 70’s, buildings became more air-tight to reduce energy costs associated with escaping heated or cooled air.  But then occupants began developing health problems, and researchers determined that decreased air flow in buildings led to higher concentrations of carbon dioxide and volatile organic compounds (VOCs) in the indoor air.

Three of the VOCs NASA focused upon in its research were benzene, tricloroethylene, and formaldehyde.  These chemicals pose various health hazards that range from skin and eye irritation to headaches, asthma, and cancer (pp. 3-5).  Assuming we’d like to avoid these health hazards, what can we do to reduce the levels of these chemicals in our homes?

As NASA points out, “The first and most obvious step in reducing indoor air pollution is to reduce off-gassing from building materials and furnishings before they are allowed to be installed.” (p.2)

The best way to reduce chemical indoor air pollution is to choose lower-VOC or zero-VOC options for furnishings, floorings, and other elements inside your home (wall paint, flooring glues, shower curtains, etc).  That way, you’re bringing less VOCs into your house to begin with.  (There are lots of good articles about this on the web; I encourage you to Google-Fu them.)

In addition to reducing VOCs by using less-toxic cleaning supplies, lower-VOC paint, etc., we figured “If it’s good enough for NASA, it’s good enough for us,” and bought houseplants – lots of houseplants.

Before I bought the plants, I did an online search and found many helpful articles.  This article at has a graphic of various houseplants and the chemicals they filter best.  And since houseplants have not fared well at my house in the past, I also read articles, including this one, on low-maintenance, hardy houseplants.  See this article for a good overview of the benefits of houseplants, including how many you need per room/ per square foot.

In the end, I decided to buy plants that didn’t have runners that would wind up all over the house (I’m looking at you, golden pothos).  I found a local nursery and selected plants for various rooms based on the available sunlight in those rooms, the amount of available space, and what looked good to me.  Be sure to check how big each plant typically grows, so you don’t buy ones that will outgrow the space you bought them for.

For the bedroom, I selected a snake plant (a.k.a. mother-in-law’s-tongue; see picture at top of post) because they are one of the only plants that continue to take in carbon dioxide and give out oxygen at night.

So far, it’s been about six months and none of the houseplants has died.  In fact, nearly all of them are thriving.  It’s hard to say whether our indoor air quality has improved, since we don’t have a way to test it.  But at least we know that science is on our side, and we didn’t waste our money on air purification myths like beeswax candles or salt crystal lamps.

CAUTION: Many low-maintenance houseplants are toxic to dogs, cats, and sometimes children if they chew on the plants.  If this is likely to happen in your home, make sure you know which plants are toxic, and put them where pets or children cannot reach them.