Indoor Air Quality Do and Don’t List

Indoor air quality made national news today, and building scientists (including us) are all thinking “Finally!”. Finally, people will be aware that indoor air pollution is a problem – as important as outdoor air pollution. That what we breathe is as important for health as what we eat, drink, and touch. And then, ask the question: How we can we know whether the air inside of our homes, workplaces, public buildings, is safe to breathe?

Before you reach for your favorite search engine and pull out your wallet, here is a ‘DO’ and ‘DON’T’ list to give you control over your indoor air, and not just waste money on the first shiny technology at the top of the Google page. This list is based on our experience and education in building science, design and construction — along with and dozens of air quality analyses and equipment tests. It will save you time and money.


  1. Find out what’s really going on in your building: Enlist the assistance of a building scientist. In buildings, air flows and pollutants can come from many complex interactions. Using a scientific, data-driven analysis approach, the true causes can be discovered and real solutions can be implemented. Look for BPI and Healthy Homes certification and at least a few years of local experience, and also look for low or zero conflict of interest. If your analyst is selling stuff, that can be a conflict of interest.
  2. Get a good carbon dioxide monitor. High levels mean you are breathing more of other people’s exhalations (and other air pollutants, too). Levels in the mid 400’s to 700’s indicate that room air ventilation is pretty good. Above 800 indicates that additional ventilation is probably needed. Open windows, doors, if this is the case. We like the Aranet monitor (around $250) because it’s easy to read and portable.
  3. If you have any fuel-burning appliances (gas stoves, fireplaces, or open draft water heaters or furnaces), be sure you have carbon monoxide monitors. Ideally, the monitor should show low-part per million (ppm) readings. Most code-required monitors only go off at around 70 ppm but low dose, long term carbon monoxide levels as low as 9 ppm can make you sick. There are many online. We like the X-Sense battery operated monitor.
  4. Every home in Radon zones 1 and 2 should have continuous radon monitors. Radon is really bad for your lungs and heart. We like the Corentium battery operated monitor. Again, handy and easy to read. The long term average reading over a winter and summer (nine month period) should be 2 pico-Curies/liter (pC/l) or less. If it’s not, your home probably needs a radon mitigation system.
  5. There are good air purifiers on the market. The best of them work by entrapping tiny particulates and dust as air moves through a MERV 13 or higher quality filter. How effective they are does not necessarily track with how expensive they are. What matters most is how much air makes it though the filter media. We love the DIY Corsi-Rosenthal cube – it’s easy and inexpensive to build yourself and is super effective. I’ve got one in my own house and have tested it under multiple scenarios. It works as well as a good market rate consumer grade purifier.
  6. Look for and solve moisture infiltration problems that can lead to biological infestations like pests or mold. And know that any remediation company that does not diagnose and solve moisture issues, is likely setting the stage for reinfestation. Moisture issues can be tricky and a building science based solution has the greatest chance of success.
  7. If you are experiencing high levels of carbon dioxide, carbon monoxide, radon, particulate pollution, moisture, see Step one above before you implement anything that could cause unintended consequences, like the ones listed below.


  1. Don’t use any ‘bandaid’ approaches like spraying chemicals. Beware of sales pitch words like ‘organic’ or ‘EPA certified’. These terms may not mean what you think they do.
  2. Don’t use any consumer grade air purifiers that are marketed as ‘ultraviolet, ionization, ozonation’ or other fancy scientific sounding terminology.
  3. Don’t rely on a company that sells particular products or technologies, in general. A building is a complex system of systems. Changes to one system (eg ductwork or crawlspaces) that seem beneficial, can end up creating unintentional negative feedback loops with other systems (eg attics or building equipment). Most companies that sell one type of system — and may even be experts in that system — do not understand the way other types of systems may be influenced (and, indeed, have little or no incentive to do so).
  4. Don’t mix chemicals and fancy sounding air purification technologies – including simple cleaning products or detergents. You can, literally, poison yourself and your family if you do so. Air chemistry is complex and occurring all around us, all the time. Anything that is an oxidizer (bleach, ozone, many cleansers) can speed up indoor air chemistry, resulting in dangerous airborne chemicals that can make you sick or create strange odors. The presence of moisture, combustion gasses, or heat may exacerbate these outcomes.
  5. Don’t complete energy efficiency work before you understand its impact on indoor air. This is a huge topic, and an important reason to, again, first employ the expertise of a building scientist.
  6. Don’t play guessing games. It will be expensive to undo things done in the wrong order, and in some cases, making the wrong move can embed long-lasting negative outcomes into a building that can only be solved with partial demolition.

We’ll be completing in depth blog posts on each of the topics above, and more, in the coming weeks. Air quality analysis and improvement is a complex and evolving science, but basic building science principles (like the Second Law of Thermodynamics) are tried and true for predictable, safe, and cost effective solutions. The good news is that these same principles can simultaneously address air quality, energy efficiency, and investment-grade capital planning. 

Stay healthy! Stay safe! Use building science.

Links: We do not accept payment or any other incentives to provide links for any product recommendations. These are here because we’ve had success using them for our clients in Southwest Virginia, and have real world experience with them over that past several years.

DIY Corsi-Rosenthal Air Purifier:

Carbon Dioxide Monitor:

Carbon Monoxide Monitor:

Air Purifier (not DIY):

By: Monica Rokicki, Founder and CEO


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