Interesting CO2 consistent readings

#1

Everyone has been out of the house for a week now and I just got home and checked the monitor. I found this interesting how smooth and consistent the CO2 levels are. There are no spikes and other abnormal highs and lows. This seems to show that the readings are accurate (at least relative to itself). I also found it interesting how they rise and fall slightly throughout the day. You call also see the moment I got home by the spike at the end.

Just thought it was interesting. Any thoughts on the rise and fall throughout the day?

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#2

Thanks for sharing this! Your observed daily CO2 pattern might be influenced by photosynthesis of nearby plants such as trees. During sunshine, plants absorb CO2 for conversion to sugar. The CO2 uptake ceases at night.

#3

We do have house plant, not a whole lot but a few. That would make sense. If that is the case, that is interesting how a few plants can have an impact on the CO2 levels.

#4

It is indeed fascinating! Motivated by this post, I read a bit more about this topic. Some thoughts are shared below in case someone is interested.

I found a conference paper where CO2 uptake by indoor plants was studied, depending on different light conditions. Table 1 emphasises the total of CO2 which can be absorbed by room plants in one day:
https://www.google.com/url?sa=t&source=web&rct=j&opi=89978449&url=https://www.matec-conferences.org/articles/matecconf/pdf/2017/17/matecconf_iscee2017_05004.pdf&ved=2ahUKEwjq7I3XuoiJAxXNTkEAHUSmDy4QFnoECDkQAQ&usg=AOvVaw0wuT7MGYwqw6jSlrROX4_7

A tree absorbs around 10 to 40 kg of CO2 per year, according to EcoTree:

This translates to around 50 g of CO2 per day, which means around 50 g of synthesised sugar (the carbon mass fraction in CO2 is similar as in sugar). Using the ideal gas law, the 50 g of CO2 correspond to roughly 6 liters of CO2. Let’s assume a 3m x 3m x 3m bedroom with a total volume of around 27’000 liters. In this case, 6 liters of CO2 would imply around 200 ppm of CO2 which are absorbed by one tree in one day. Normally, people do not have a tree in their bedroom, so let’s divide by 10 to account for a smaller room plant. This gives us 20 ppm.

My very rough estimate is in the order of magnitude you observed. However, I assumed your bedroom is perfectly sealed, which is inaccurate. And plants not only absorb, but also emit CO2 (day and night). They synthesise sugar for a reason => to use it. The 20 ppm potentially overestimated the net CO2 uptake of a room plant in a bed room. I suspect your CO2 pattern is influenced by indoor as well as outdoor plants: the individual contribution depends on the number of outdoor and indoors plants, the light conditions and how well your house is sealed.

#5

I’m sure it has to be more than just the indoor plants as the monitor is centrally located within the main part of the house. This area is quite large and the room height is 2.5x normal, so cubic foot wise, it’s big. Another note on the room, it has very large southern-facing windows that allow a lot of natural sunlight in the room. We have a lot of trees around the property and I can only assume the house is not air tight. However, since no one was home, no door nor window has been opened for 5 days.

#6

Not only do plants stop sequestering CO₂ at night, but them & other organisms (bacteria, fungi) continue emitting CO₂ as part of their biological cycle as well. I live near an old forest and observe roughly 50ppm, rarely up to 100ppm variance between day and night on my outdoor sensor.

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