My Air Quality Stinks – But Now We Can Measure It – Porch Paint, VOCs, and Ventilation


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If you’ve ever painted a room, you know it stinks. Well, the job isn’t so bad, but the smell can be. The real problem, it turns out, comes down to letting the chemical pollutants (VOCs) vent outdoors, rather than getting stuck indoors. Thanks to new Indoor Air Quality (IAQ) monitors, I have data on this! Thanks to apps, I can show you how the different devices performed as well.

A quick definition. Volatile Organic Compounds (VOCs) are sometimes called chemical pollutants. Basically, they are any chemical you can smell and that is organically based. This means their boiling point is close to room temperature. They also tend to be highly reactive and create new, nasty chemicals when allowed to play with other chemicals. Gasoline contains VOCs, many paints and cleaners contain VOCs.

I’ve spent much of the last year wrapping my head around Indoor Air Quality. This weekend my wife, who loves to paint, decided to tackle the floor of our front porch. (Somebody is going to ask, it’s Sherwin Williams porch paint. Thick like pudding. Nice to work with. Pretty stinky.)

I’ve been collecting IAQ devices including a Foobot, Awair, NetAtMo, Air Mentor, Speck, a few temperature and humidity monitors, and a very sensitive carbon monoxide monitor. They live in my living room right now about 30 feet from the front door and front porch.


My favorite one so far is the Foobot, a French startup (full disclosure, Foobot has given me monitors to play with and learn from after I bought the first one.) I’ll be writing reviews on the various monitors in time, today I’m focused on one specific event – painting the porch.

The biggest reason I like Foobot is their pro-only dashboard. The app has a nice interface, but for professionals there is an online portal with much better analytics and an easier to interpret chart. The professional dashboard makes it very easy to see changes over time. It’s also great for comparing multiple devices, but I won’t dig into that today. Here’s a pro-dashboard screenshot of the VOC graph for the weekend of the paint job:

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Reading the Chart

Note how in the first 24 hours of the chart VOC levels are low, well under the 300 parts per billion (ppb) threshold that Foobot uses. About noon on the second day my wife started painting. The spike wasn’t quite as high because the front doors weren’t open (my house used to be a general store and has 3 front doors, 2 are operable.)

Then we opened the front door around 4 PM and levels dropped while the front door was open and the first coat was drying. Then Rachel really started slathering the paint on with the door open and the fumes rushed inside, making the Foobot glow orange (meaning bad, blue is good.) Levels spiked.

It was time for bed, so we closed the doors. Levels went down temporarily, but then spiked and plateaued at a high reading. The weather was mild that night and the windows were closed, so the VOCs from the paint stayed in the house and the levels stayed high. Thankfully upstairs we had windows open as we slept, although it froze us out at the end of the night as temperatures dipped into the high 40s. If I was smart enough to put a Foobot upstairs I’d know for sure…

At about noon on Sunday I opened the doors up and VOC levels plummeted to normal levels. The low reading for Foobot is 125 ppb. It got close to that reading. It wasn’t particularly windy in the afternoon, so levels started to go back up a bit probably because the air wasn’t being changed. Then levels spiked as I closed the doors again. I opened the doors up again Monday morning, you can see the spike drop off at the very end. It’s an example of how a fresh air system aka mechanical ventilation can be helpful. The weather isn’t always good enough to open doors.

Monitor Differences

This was also an opportunity to look for strengths and weaknesses in my collection IAQ monitors. About 80-90% of the time the monitors alarm, I have no idea what the cause was. This time I did.

I found some strengths and weaknesses. For VOCs, Foobot appears to be the most trustworthy. (I think, as I don’t have a high end monitor to test against.) Here are the IAQ devices at 9 PM. Only the Foobot is showing a problem, it’s full orange. Full blue is happy.


From left to right in the back row are Foobot, Awair, Speck, NetAtMo, and Air Mentor 6 in 1. In front are a simple temperature and humidity monitor and a CO Experts carbon monoxide monitor.

Here are screenshots of the devices at 10:42 PM, right about the time of the first high spike.



Foobot measured 1192 ppb of VOCs. Dust levels are relatively low at 11. 25 is the threshold (micrograms per cubic meter is the unit, but it doesn’t matter here since all devices use that metric.) The carbon dioxide (CO2) measurement is a proxy of the VOC sensor, so it’s untrustworthy at these VOC concentrations. It’s best to ignore the CO2 reading of the Foobot, actually.



Awair uses an index rather than a ppb reading for VOCs. It should be spiked at 5, it’s not. Not a good sign. Also note it measures relative humidity to be 10% lower than Foobot. The dust measurement lines up, 11 vs. 13. Close enough for these consumer level devices. The CO2 reading seems realistic. The lack of accuracy of the humidity and VOC sensors reduce my confidence in this device.



The NetAtMo is more of a weather station with a carbon dioxide sensor than a true IAQ monitor, but it is generally a very nice device. You can see the high and low for that day and that the temp is 58 and falling. The 616 CO2 reading jives well with the 552 from Awair and seems realistic since base level at my house is around 450-500 because of exhaust fumes from the road in front of my house. 37% relative humidity is fairly close to the 32% of the Foobot.

Air Mentor 6 in 1


The Air Mentor 6 in 1 (there is a less expensive 4 in 1 model) roughly lines up with CO2 and humidity levels. The temperature is on, too, 23.4C equals 74.1 Fahrenheit. It obviously has not been optimized for American use.

On VOCs and dust, it falls down pretty badly. PM2.5 is particulate matter 2.5 microns or less, otherwise known as dust. This is small enough not only to inhale, but potentially to go into your bloodstream. PM10 is 10 microns or less, that’s the size that is inhalable. PM2.5 is what Foobot and Awair measure. Air Mentor consistently does not read dust. Much of the time it reads less than 1 while other monitors are in the 10-20 range. Not good. On VOCs it has proven insensitive as well, as you can see here, reading 200 vs. Foobot’s 1192. I’m pretty unimpressed with this device, as was my client who bought it and lent it to me.

Comparing these consumer Indoor Air Quality monitors has been tricky, each one measures something different, and each one has different strengths and weaknesses. In my opinion Foobot performed best in this instance, barring CO2 which it doesn’t actually measure directly.

Conclusion: Ventilate, Ventilate, Ventilate

Judging by how much the readings went down when I opened the doors of the house, I need more ventilation. Quite a bit more.

I’ve become a big fan of data over the last few years. The more I dig into it, the more I learn. While I know in theory that bringing fresh air into a house is a good thing, it’s fascinating to watch it in real time with IAQ monitors. More often than not, my assumptions get broken. In this case, my assumptions were confirmed: ventilation is good for every house, even one still a bit on the leaky side like mine.

This was an interesting confirmation for a guy with a healthy streak of doubting Thomas in him. I want to put my fingers in the holes – prove it to me. I’m glad my wife decided to pain the porch and provide this great opportunity! Every one of our clients gets a fresh air system recommended to them. I’ve studied IAQ pretty hard for the last year or so. This was a golden opportunity to measure IAQ with multiple monitors and a major event.

I also have the words of Jeff Siegel, an IAQ researcher at the University of Toronto, in my mind. He presented last year at the Healthy Buildings Summit and suggested that plain old paint with plenty of ventilation is probably the best way to go because low or non-VOC paints often have other issues such as lower durability or other unfriendly chemicals. At his home in Toronto he painted his new house while living with family, letting the house ventilate for a few months. Yes, that’s overkill. For the rest of us, try to do it in nice weather and open the windows for a few days.

Now What Do I Do?

Want to find out what’s going on in your house? Buy an IAQ monitor. Foobot remains my favorite both for the device and the interface. Better still, consider adding a fresh air system which brings fresh air into your house 24/7 to dilute nasties like VOCs from paint.

Free IAQ Guide – Get the IAQ chapter of my book when it’s done. I’m working on a book about Home Performance – how to solve problems in your home at their root rather than only treating symptoms. The IAQ chapter has been extremely tricky to write because the science is still developing. The interface with insulation, air sealing, and HVAC makes it even more complicated. Get a free copy when it’s complete, and a sneak peek of the fresh air system/mechanical ventilation chapter too!

Thinking of Buying an IAQ Monitor? 

If you found this article helpful and plan to buy one of the devices reviewed, would you be so kind as to buy one with the following links? They’re the same price you can buy them elsewhere and I get a commission. I don’t get paid for this research. Buying from here will help me keep the bills paid so I can keep writing about IAQ. Thanks in advance!


Read my full review on these devices.

Post Script: Throwing Down the Gauntlet for Pros

Lastly, I’m going to throw down the gauntlet. In our practice we recommend a fresh air system to every client. If you are a fellow Home Performance or HVAC practitioner and you don’t at least recommend mechanical ventilation, you are just pretending. Mechanical ventilation is not an unnecessary additional cost, it’s something that comes with a great deal of value if we take the time to educate our clients about it. We need to stop talking about fresh air systems like they’re a bad thing, and change the dialogue. Indoor Air Quality events like painting happen. Cooking and cleaning happen all the time and affect IAQ. Our minds function better with fresh air – one of my client’s children competes at Rubik’s cube competitions and has proof his times are faster with lower carbon dioxide levels. Let’s tell the stories. Then recommend fresh air to every client, regardless of air tightness or their likeliness to do it.

Further Resources

My full review of these IAQ monitors. I compare them on over 20 attributes.

Dr. Jeffrey Siegel on IAQ Radio – I met Jeff at the Healthy Buildings Summit where he was keynote speaker and shared a few meals with him. I really like the way he thinks and the simple way he breaks things down. In this episode he focuses heavily on filtration, which has heavily influenced my thinking. Energy Smart is doing a Habitat for Humanity project currently, we specified a standard heat pump, not a mini split, because we wanted better filtration. Jeff’s thinking was a big part of why we did that. IAQ Radio is a delightful resource as well. Listen to Richard Corsi, Joe Lstiburek, Bill Rose, Jordan Peccia, and Lew Harriman at a minimum.

Air Quality, Your Health, and Energy Efficiency – A nice 16 minute intro to IAQ and the building microbiome with Dr. Siegel.

Photo Album of IAQ Devices – I’ve been keeping an album of the IAQ devices I have: Foobot, Awair, NetAtMo, Speck, and Air Mentor. There’s a little commentary, but not much. Feel free to use any pictures with attribution to this blog entry.

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