Indoor Air Quality Indicators and Measuring Them

The issue of Indoor Air Quality in a home comes up very regularly for a Home Energy Auditor.

People work hard to keep their homes clean and to serve healthy food from their kitchens. We also want to know the air we breathe in our homes is healthy. There are a lot of things out there to spend our money on like, air cleaners, fancy filters, ozone and UV lights to start with.

What types of things cause a home to have un-healthy air?  A recent presentation to the Indoor Air Quality Committee at the EPA used this slide from a researcher at the University of Pittsburg.


What I see as important about this list is that these are measurable. A Thermometer and a Humidity meters are commonly found in many homes. Most homes have a CO Detector for Carbon Monoxide and a lot will have a CO2 detector for Carbon Dioxide.  That covers 50 percent of the items in this list.

What is left are things like small particles, Ozone, volatile organic compounds and formaldehyde. Small particles can be a tough one because we are talking really small.  The standard size we look at is 2.5 microns.  A human hair at 50+ microns gives one a size comparison.

The others are gaseous in nature. Much of these gases can come from materials in the home or the the furnishings and are released over time usually referred to as ‘off gassing’.

As a family lives in a home, things change.  You go in and out, opening doors, windows, cooking, living, enjoying your home. How do you keep track of the air in your home? How do you know it is good, or that you may need to do something to fix a problem?

For years homes have had thermometers and humidity meters available.  Now there is a whole new series of measuring instruments to monitor these various indicators. The simple detector technology for Carbon Monoxide has been improved to respond to a range of levels and actually measure the gas. The other gasses have the same technology.

NOTE:  This measurement technology has been available for professionals at a significant price. Now the progress has made the units smaller and more affordable.

My friend Nate Adams has been doing some major work in existing homes. Nate works in the Akron Ohio area.  He has moved his business from an Insulation Contractor to a full service home performance contractor.  Recently, he has been exploring how the energy efficient features he is installing also improve the quality of the air inside those homes.

Nate has written a blog post reviewing some of these newest monitors to provide homeowners with a comparison of the available offerings.

I was challenged to write this post explaining my reaction to Nate’s Review.  My initial reaction was ‘disappointing’.  Nate’s challenge was ‘Why”.  So here is the why.

First:  While the technology for detecting has moved to measuring, it still has a ways to go.  Partly technology and partly continuing to reduce the cost.

Second: There is a very limited offering. Seven Products were reviewed and three more were mentioned, but lacking the data logging feature. I was hoping for a few more.

Third: Each entry reviewed had pros and cons.  I do not feel that any single item is a comprehensive monitoring solution.

Because I chose to wade through my reactions and thoughts, it has been a good exercise for me. Writing down my thoughts and reasons really helped me look at my initial response of disappointment and why my reaction should be more then that.

My second reaction after working through the above is ‘hopeful excitement’.  While we may be disappointed in the number of monitors and the comprehensive coverage;  we should be looking forward to the future developments and monitors that measure more.

The challenge of these developments and the potential they hold are very interesting.  What can we do?  What should we do?  I suggest that realizing the potential is in many ways up to us. Those in contact with the public, the home owners, or renters. We need to advocate for measurement and then taking action based on what the monitors reveal.

11 thoughts on “Indoor Air Quality Indicators and Measuring Them

  1. David Eakin

    John – your last paragraph is the one of most concern to me (and I also raised on Nate’s blog). What are the universally-accepted (not individually-“opinionated”) measures that require action? If you take the current ASHRAE guidance at face value, you just implement mechanical ventilation – whether or not any testing has been performed; whether or not any testing shows anything requiring mitigation; whether or not the incoming air is proven to be better than the interior air being exhausted. Just do it. I suspect that even houses built to the Passive House standard will leak enough “fresh air” that any indoor monitoring will show minimal levels of “pollutants” (I put quotes here because temperature and humidity levels are not pollutants, but preferences), or levels that can be remedied by much more reasonably-costing recycling filtration units and (where needed) dehumidification units outside of the typical residential HVAC systems. But it will never be proved one way or the other until monitored.

  2. The Energy Guy Post author

    David, My question is more about the concept of just monitoring or doing something after the monitor says there is a problem. Different families will evaluate the data and make different decisions. The challenge that we have is how do we discuss these measuring devices, what recommendations will we make?

    Also, if a family believes the outside air is a bigger problem then inside air, then an experiment is in order. Buy the monitor of your choice and set it up outside for a week. Then move it inside for a week. Compare the data logs. Make your own decision.

  3. Nate Adams

    David, are you going for a wet blanket award or something? I don’t know that I’ve ever seen you say something positive without a major qualifier…

    The standards for IAQ are not well understood yet, we need to do as you say and monitor. These devices give us a decent, if not great, way to do that. If you were king, how would you do that?

  4. The Energy Guy Post author

    David, A Universally accepted problem with Indoor Air Quality is one that causes a resident a problem. If your home is growing mold, and one of the 5 people in the house is sick. You remove the person or you remove the mold. If you choose to remove the mold, you would be wise to also fix the problems that created the mold. If no one is sick, then the mold will cause someone a problem when the house goes up for sale. The home inspection, realtor or home buyer will see it, smell it and it will get removed and perhaps the problem fixed or the price of the house will go down. I wrote this last night and deleted it. I would welcome some serious discussion about how we as industry professionals can move this along.

  5. Nate Adams


    Well said that an IAQ problem is one the client tells you exists.

    It’s our job as Building Scientists to help create an environment where good IAQ happens naturally, usually with a good shell and the right HVAC (after solving bulk water problems.) We are in the business of solving problems. I’d like for more people to know about us. These IAQ monitors give another onramp to what we do.

    Thanks for pushing through your initial gut reactions. I too am excited for what these devices could bring. We have to work with what we’ve got, and they are finally adequate (more or less) to be used as simple diagnostic tools.

  6. John Lapotaire

    This is a great discussion but one that should be approached carefully. Having said that let me explain a bit further. The issue with most regarding the collection of these indoor environmental measurements is that most will have no idea what is causing the possible elevation let alone what an elevation actually is. In many cases the occupant will have preconceived ideas about what the issue is and will be simply looking for support of their opinion. Not very scientific and can lead to additional problems.
    While I do like the ability for a homeowner to collect background information on their home, we must remember that it’s extremely difficult if not impossible for the homeowner to accurately interpret the results.
    We often see the homeowners collect the data and then ask their HVAC contractor to interpret the results. This leads to expensive bells and whistles for the homes HAVC system that will most likely have little or no direct impact on the actual indoor environmental issues. For example, the magical UV or purification systems that can have a measured negative impact on the home when dealing with sensitive occupants. Let’s face it we are dealing with the one percenters here, not the regular Joe.
    Long story short, this is a great conversation and a great look at the complexities of residential IAQ and the limitations on the data loggers and the homeowner’s ability to interpret what can be very misleading information.
    Just my opinion from the cheap seats………

    1. The Energy Guy Post author

      John, Thanks! You expanded on my last paragraph about where we go from here. Part of this is deployment of measuring instruments. Part of it is why homeowners should buy one. Part of it is where does the service and follow up come from. Some of that may well be ours. Some of that is up to the manufacturer of the instruments.

      As to who should be interpreting the results, anyone except some one with products or services, for sale, on their shelves. Like your tools, if you only have a hammer in your toolbox, screws are treated like nails.

      This is why I added the last paragraph. Keep your ideas coming. Tell the others you know to chime in. Here or on Nate’s original post.

  7. Andy

    I’m presently using a foobot to measure with. Since I know co2 is inaccurate (a calculated number and not measured) . I also place 3 meters that specially measure co2 on the same kitchen counter and they all read much lower than the foobot.

    My next recent experiment. I moved the foobot to the outside (almost outside, the site is filtered to about 10 microns first). If the foobot is even in the ball park on voc’s my outside air is way worse than my inside Air.

    I’m looking forward to being able to control ventilation both on the indoor air vs the outdoor Air. Ramping up the ventilation when indoor air gets bad (whatever this means) might actually make our indoor air worse.

  8. The Energy Guy Post author

    This comment was made on a Energy Professionals Forum. I am posting Eric’s comment here to keep a good record for my Blog readers access. JN

    Eric Kjelshus, is a HVAC Contractor in the Metro KC Area. you can find him on the web at has a quick snap shot test or leave it there for week. Good looking reports that can be emailed or printed, on a very base report. hand held quick test or but not a good report, I have to write it up.

    Fluke 975 AirMeter pricey no report but on high end

    I like to take care of all 22 base things before I do a lot of testing. If the water heater is back drafting just take care of it 1st before spending 2 weeks on seeing how border line it is. Each time I work on a gas/LP/ burner I test CO, CO2, dew pt, temp, draft. just makes good sense to take care of big things.

    Xmas I unwraped paper for kids – The VOC’s went to 3400 PPM from 39 I had no way of knowing till testing

  9. David Eakin

    John et al,
    Sorry I have not been monitoring this blog as closely as I should. John – I am in agreement with you on the need for affordable, accurate measuring devices that inform the occupants of any dangerous or unhealthy environment. We currently do not have such devices. We do have a huge push to provide external mechanical ventilation as a remedy for all ills with a “just trust me” guarantee. This is what I am balking against. Will the definition of “unhealthy” be dependent on the occupants’ sensitivities? Sure, but there should be some universal base lines (your inclusion of the excellent Pitt chart seems to point to them). So if you take this chart as a “strawman” base, there are 8 things that need to be constantly monitored in interior air; as you said – 2 of them (temp, relative humidity) are fairly easy/inexpensive to monitor ACCURATELY; the others, not so much (I even see that Corbett Lunsford is using a more accurate set of metering devices for CO in his tiny home travelling lab than what is commonly available so that subtracts from your availability). Are the CO2 monitoring devices any more accurate (and affordable)? Don’t know. Why not a single device that monitors all 8 items and sounds an alarm (or sends a WiFi alarm) and an indicator of which sensor has been triggered? TBD. Until then, recommending any course of remedial or preventative action is more myth than science. And prescribing a universal solution right now (external mechanical ventilation) is the myth.


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