I have a new DIY Airgradient ONE. I’ve just turned it on for the first time tonight.
It will never be taken outside.
What are the exact things I need to do to calibrate it and maintain it so that the CO2 readings are accurate?
The only thing I’ve done so far is turn off ABC. Is that enough to have accurate readings?
I would bring the sensor outdoors and let it sit powered on for 5-10 minutes. Then initiate a CO2 calibration on demand, through the AirGradient Dashboard site.
Once that completes, let it sit another 5 minutes or so, then unplug it and bring it inside, trying not to jostle it too much. Power it back up and it should be accurate. If your house is tightly sealed, then disabling ABC will keep it accurate for longer, assuming you never see it return to around 400 ppm on its own.
I have one in my basement and it almost never gets below 800, so I disabled ABC, and every other month or so I bring it outdoors to calibrate again. It usually changes by less than 50 ppm, compared to one sensor I have that I have not disabled ABC, and it gets off by 200-300 after a week.
I think this is a great answer, and that’s what I would say, too.
Initially, it’s best to take the monitor outside briefly (using an external battery if there is no socket nearby) or at least place it on a well-ventilated windowsill and exit the room to calibrate it. If ABC is disabled, this should allow it to remain accurate for a few months.
With this initial calibration, place it in its permanent location and see if the readings ever drop to 400-420 ppm (if they go lower, you will want to recalibrate as it means your initial calibration wasn’t great). If the readings drop to the 400 - 420 ppm range when you go out to work (for example), then keeping ABC on should not be an issue. However, if the readings never drop that low, you will want to disable ABC and manually recalibrate the monitor outside every few months.
Thank you both!
Could you please elaborate more on the 400 number as it relates to being accurate or not?
Are you saying that if it is accurate, it should reach 400 on its own sometimes when people are not around – and if it never reaches 400 when people aren’t around then it’s inaccurate and requires recalibration?
The worldwide average is around 427
When you do the ABC, it resets whatever it is currently reading to become 400 and then adjusts higher and lower as the concentration increased or decreases. Since the outdoors are incredibly unlikely to go below ~400, if you see it doing that, then the calibration is inaccurate and needs to be adjusted.
It all comes down to your home. My family could leave for half a day and the CO2 would go from ~1200 - ~800, but it takes my home multiple days for the indoor sensors to read anywhere close to 500. In homes that have more natural ventilation (air leaks) it may happen much quicker.
Since mine doesn’t naturally get down to anywhere close to 400 over the course of a week, the automation correction ends up being incorrect. But if your situation does allow that, then ABC should be fine to enable.