I have two indoor units. One, in my bedroom area (20x20 plus hallway, bath, etc). The other In a downstairs open area 2000+ sq ft, high ceilings. The readings are usually 500-650. But twice I have had times where the readings jump to 1100-1400 for days at a time. One of these times is now, the other just before summer. (after a week or so it went right back to normal) I am the only person in the home.
No appliances running, whether the hvac is running makes no difference. There have been times of normal readings with it running or not. Right now, the weather is cloudy and raining so the hvac hasn’t been running. A couple days ago I saw the readings shoot up from 550 when I went to bed to 1100 when I got up. The other monitor was high as well. Yesterday afternoon, I opened all the windows, doors for over an hour and let the wind bring in fresh air. I put the monitors outside and recalibrated them. I had the “use default configuration” option on but switched it to “off”. This morning when I got up, both monitors were at 1400. That seems crazy as I’m the only one in the home right now and for months in between the last high readings it’s been in the 500-600 range 24/7.
Any ideas or advice would be appreciated.
Do you happen to remember what the CO2 levels were shown after bringing it outside before doing the calibration?
With the default calibration of every 7 days, it uses the lowest value seen to be “400” and everything is based on that until the next cycle 7 days later.
My house is pretty tight and it rarely gets under 900 and spikes beyond 1800 at night with 4 people in the house and people here nearly all the time. This means eventually calibration sets that to 400, underreporting by 500. So I would eventually get readings that were very low all the time, since it was 500 points too low. When I bring the sensor outside I would get readings of 50 or something silly like that.
So I turn off auto baseline calibration and bring the sensors outside every few months to set them manually.
I suspect you may be having a similar situation where you are used to the 500-650 readings but they may have been incorrect for quite some time and now you have it calibrated properly with 1400 being a more accurate representation. But I could be wrong.
You could do another cycle of taking the sensor outside for 10 minutes and see if the CO2 goes to around 400 without anything else. It could be a touch lower or could be nearer to 500, but if you get much lower than 380, then it needs calibration.