AirGradient Forum

Could sewer gas increase CO2 and TVOCs?

#1

My unit has been operating well, thank you. I do shut my WiFi off overnight so there are some gaps in the data.

For the past 5-6 months I’ve noticed an increase in CO2 and TVOCs. I’ve pasted the CO2 week chart below. ChatGPT says there is some correlation. Both values drop when a door and window are opened.

I changed both the gas furnace filter and fresh air ventilation filter on Sept 4. I will take the AirGradient outside today to let it recalibrate. I have a couple of situations that might be contributing, including a powder room that has been left demo’d for a few years (toilet reinstalled - unused - flushed occasionally, sink drain covered in plastic), a first floor laundry drain that has an odor when the washing machine is used, the washing machine door that is left open to let it dry after a wash, and there may be other sources…

Nothing has really changed over the past year so this may be difficult to track down. From what I read best approach may be to let the sensor calibrate, then move it from one room to another, I guess on the same day when the reading is high, to try to narrow down the source. First I might just open things to get good readings, then close and see how long it takes to increase.

Am I correct to include sewer gas as a possible source? Am I on the right track generally?

TIA.

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#2

Opened everything up for a time, then closed. The readings rose steadily:

1:00 pm 762 156
1:34 835 179
2:43 932 194 opened again
3:27 874 144

Then later I realized I have been leaving the washer detergent tray and door open to let it dry between washes. I closed them, we’ll see if that makes a difference.

#3

I could see TVOC maybe increasing with a sewer drain open, but I wouldn’t expect CO2.

In what room is your sensor located? I see regular increases in CO2 on the sensor in my bedroom where we sleep in a room with a closed door. Once the door is opened and people are moving around, it decreases in that room. If the house becomes vacant mid-day that would also contribute to CO2 levels decreasing even more.

#4

The sensor is in the living room on my desk. I sleep with the bedroom door closed.