In the recent issue of Make magazine they had a comparison of hobbyist CO2 sensors. The purpose of these meters was to help identify indoor spaces that might be more conducive to Covid spread (higher CO2 levels in a room with people means more shared air).

I decided to build one for my office because I share a small 10×12 room with a coworker. I thought seeing the CO2 might be interesting and informative… I never got that far:

What I didn’t expect was to see that my own home is quite poor when it comes to CO2 levels.

Our house is on a busy road, the traffic noise can be difficult to ignore so we often run the HVAC 24/7 even in moderate temperatures. Our house is a 1989 build, it’s all original — doors, windows, siding, etc — the HVAC is replaced but with “like kind”, meaning there’s no ERV/HRV add on, though the new heating appliances are high efficiency so they have dedicated combustion air ducts (instead of drawing air from the house).

Our house is consistently in the 800-1200ppm CO2 range when the windows have been closed for a few days. I personally haven’t felt that it was stuffy or recycled feeling, but the data doesn’t lie.

The other interesting aspect is just how much our gas range will impact CO2 levels… take a look at this annotated chart:

The oven running spikes the CO2 way up. I’m definitely making it a point to keep windows open as much as we can, even if the HVAC is running, to keep some fresh air in the house.