AirGradient Forum

Best IAQ monitoring options for an aggressively oversealed apartment

#1

So I live in a condo unit that:

-Has no direct openings to the outdoors. (Yes. It has no opening windows and they cannot be added).

-Uses an HVAC system that pulls in no air from the outdoors. It only pushes air out through the bathroom fan to create a negative pressure, thus trickling “fresh” air from the building hallway.

-Has a “fresh” air short circuit, so a portion of new air is typically exhausted immediately before it can be cycled through most of the apartment.

-Is a new construction, so it is very tight.

As you can imagine, the air quickly becomes VERY stuffy, smelly, irritating, etc.

I used an Airthings IAQ monitor for awhile, but eventually gave up on it due to it’s company and documentation being very opaque and unreliable in regards to how it gets it’s readings.

I’m exploring an upgrade, and Airgradient One is my favorite option so far. A concern I find myself too uneducated too alleviate, though, is in regards to calibrations. It seems every one of these monitors calibrates at some point or interval, and that calibration assumes a baseline of, say, being operated in an indoor space where air can be regularly refreshed with outdoor air.

You see my problem here.

Depending on how frequently it would need to happen and for how long, I could potentially bring the unit up to my building’s common area on the roof to recalibrate. But this may be a challenge as it’s a shared space, weather and time can be restrictive, need to find a reliable power source, etc etc. I would really need to know how often I would have to be on the roof to monitor the thing while it calibrates.

All that said, could anyone here advise me on if the Airgradient One is a good product for my use case? If not, what may be? What maintenance expectations should I have before buying the AGO?

#2

Hi @windsdance, welcome to our community!

Regarding the periodic calibration you mentioned, I assume that it is related to CO2 readings.

CO2 sensors (like SenseAir S8/S88 in the AirGradient ONE, for example) have a feature called ‘Automatic Baseline Correction (ABC)’ (also called ‘Automatic Baseline Calibration’) that helps automatically correct long-term sensor drift.

Here is briefly how ABC works: Senseair ABC Algorithm – Advanced CO₂ Sensing

The ABC-algorithm constantly keeps track of the sensor’s lowest reading over a preconfigured time interval and slowly corrects for any long-term drift detected when compared to the expected fresh air value of 400 ppm (or 0.04%vol) CO₂. In normal indoor applications, the carbon dioxide level drops to nearly outside air at some point during a week. By sampling the values for an 8-day period and then comparing the lowest value with the sensor’s 400 point, the sensor can understand if it needs to adjust the zero point.

In your case, from what you described, it sounds like fresh outdoor air doesn’t have a lot of chance to get in. If we deem that it is a 24/7 occupied room, the recommendation is to disable ABC. With ABC turned off, the CO2 sensor should be manually calibrated every 2-3 years according to SenseAir’s recommendation. For a manual calibration, the whole process shouldn’t take too long, actually it takes just a few minutes, but we usually recommend placing the monitor to expose fresh air for a while before hitting the calibration button. I’d say it shouldn’t take longer than 15 minutes. You can power up your AirGradient ONE with a portable battery (power bank) during the manual calibration process.

These resources could be helpful for you:

I hope this helps, please feel free to let me know if you have any questions. Also look forward to hearing from other member community how they think.

Thanks!