It started with brain fog in my home office.
Not dramatic fog: just that late-morning feeling of being slower than I should be, in a room I spend most of my working hours in. I'd noticed it for a while but hadn't had a theory. Then Jeff Geerling mentioned the Air Lab in a post, and the idea lodged itself in my head. I began opening the window in my office and I notice my fog went away.
The Air Lab from Networked Artifacts is a compact, open-source monitor that measures CO₂, humidity, temperature, VOCs, and barometric pressure. I'd been thinking about it for a while before I finally ordered one. What pushed me over was realizing the question was bigger than just my office. My wife has had respiratory issues we've never fully explained. The kids have stretches of bad behavior that don't always have an obvious cause. We'd already been loosely planning an ERV system for the house. But before spending money on ventilation, I wanted to actually measure what was happening.
(and yes, there are thousands of other causes for respiratory issues and bad behavior, but air quality is one of the things I was thinking about - but better breakfasts have also had a huge improvement in the kids, too...)
What the Numbers Actually Showed
The first few readings were humbling. Our bedroom was regularly climbing above 1,000 PPM CO₂ at night. The younger twins' room: same story. For context, outdoor air runs around 400–420 PPM. The EPA and ASHRAE start flagging indoor air above 1,000 PPM as a sign of insufficient ventilation. Not toxic, but enough to affect sleep quality and cognitive function.
Then I brought it to work. Our breakroom read 1,400 PPM on a normal afternoon. When seven or more of us were in there at once, it topped 2,000 PPM. That's not a dangerous number in the CO₂-will-kill-you sense, but it's high enough that you're probably not thinking as clearly as you could be.
The Second Device
A few weeks later, my dad sent me a link to the Seitron BE SAFE SG CO, a personal carbon monoxide monitor. I bought it without doing much homework first. When it arrived, I clipped it on and started using it, without fully realizing that it wasn't measuring the same thing as the AirLab at all. (can I blame it on the high CO₂ in the house?)
The AirLab measures CO₂, carbon dioxide. The Seitron I got measures CO, carbon monoxide. One letter apart. Completely different gases, completely different risk profiles. I didn't actually know that when I bought it. Doh.
Accuracy
This has also pushed me to think more carefully about sensor accuracy. My ecobee has an air quality sensor built in, but the more I dig into dedicated monitors like the AirLab and Seitron, the more I understand why they cost what they do. The sensors inside are purpose-built for accuracy in ways that a general-purpose smart thermostat simply isn't. They're not the same instrument. The ecobee says "all good" when the AirLab is showing 1,000 PPM. The ecobee's sensor is probably just not sensitive enough to pick up the difference between 400 and 1,000 PPM. The AirLab is designed to do that, and that's why it costs more I assume. When I was pricing these out I found that the sensors either were $20 on Amazon or $200 in a dedicated monitor.
(and there is a chance that the ecobee is reading more of the air behind it in the wall vs the house because of where the sensor might be)
The Garage
This morning I was loading my car in the garage while the engine was warming up. I had the Seitron clipped to my tool bag right behind my car. It alarmed at 35 PPM CO. That was kinda cool that it'll make it clear I'm in an unsafe environment. I'm excited to give it a try on job sites when I'm around heavy equipment.
Where This Is Headed
We were already planning an ERV system before any of this, an energy recovery ventilator mechanically exchanges indoor and outdoor air while recovering heat. The data now makes the case more clearly. Bedrooms above 1,000 PPM at night was basically the measurement I needed.
(and yes, we can open the windows...but with allergies in the Willamette Valley, that's not always a great option...)
I've also started leaving my office door open at work, specifically to keep the CO₂ in the sub-600 PPM range. Small change, noticeable difference.
Buying the Seitron a little blind turned out fine. ...but next time my dad sends a link to a toy tool I'll make sure it's the right one.