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!

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#3

As you don’t have access from indoors, an easy option for recalibrating in the open air is to run the AG somewhere outside using a power pack if you have one. Just take the AG to a suitable location where the CO2 should be normal and then recalibrate. The AG doesn’t use too much current, especially for the suggested 15 minutes during recalibration, so most power packs should be suitable.

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#5

Hi @Rog, thank you for confirming this. I did several tests running my AirGradient ONE on a 10,000 mAh power bank (about 35 Wh), it lasted for several hours without any issues.

Hi @airsabotage, welcome to our community! Thank you for sharing your thoughts about this. We definitely want everyone (not just people who have tech skills) to be aware of air quality and have access to healthier air. However, in this case, we are discussing a case where the user would like to make sure the CO2 measurement is reliable, so it is quite technical to get there, as CO2 sensors have automatic baseline correction (ABC) enabled to manage the sensor’s drift over time. But the ABC does have its limitations in particular situations, like a 24/7 occupied space. We are happy to improve our communication to be more accessible for everyone. Thank you.

#6

@airsabotage

What you are comparing the AirGradient (AG) monitors to and your wants / use are two different things.

As I see it, the AGs are professional, highly accurate monitors with a range of sensors (I have three AG Ones, one AG Out and an AG Go). that provide the data that is for show (directly on AG One and AG Go) and viewed on the AG Dashboard. The data can be used elsewhere (such as in air pollution maps) and, most importantly, can also be incorporated into programmes / apps such as Home Assistant. HA allows the data to be used in a multitude of scenarios, not limited to just switching a device on and off.

That is a big difference to what many of the other more basic models for sale offer, many of them, especially cheap ones, with dubious quality and accuracy. By plug and play controller, I don’t know if you literally mean that you plug a fan into the device and the device switches the fan on when it detects the CO2 is at a certain level, or if the device is a sensor that uses an app to control a smart fan or a fan plugged into a smart socket etc. I currently have a Govee CO2 sensor for review and that does the same thing. It shows the CO2 on a display but, like most of these types of sensors. you still need to access the Govee app to control a smart phone or socket.

You say that you sell used models of a similar model to the $200 AG for around $50. That isn’t a very good comparison. Compared to your description of what you sell, the AGs do a lot more, with high specifications. And, of course the AGs are new, not used, which could make a big difference.
A bonus is the very excellent service Airgradient give :slight_smile:

The AGs that I have have given excellent service to date with no problems. The newest AG, the AG Go has only just come out and so it is natural that as more and more people get to use them that minor things may be found that need tweaking. The same happens with most devices and softtware.

Recalibrating the CO2 sensor, which is what this thread is about, is something I’ve not had to do yet (it’s a simple process). It’s not part of the development of an AG, it’s the CO2 sensor itself that needs recalibrating occasionally and would be the same for any device that uses the same sensor.

#8

Hi @airsabotage, thank you for your question about the pressure sensor. Please allow me to consult our engineering team for a definitive answer, and I will get back to you. Thanks!

#9

I am just an Airgradient owner and user :slight_smile:

Yes, I think that there was a bit of a mix up. I think I understand what the type of device is that you are talking about.

I assume that it is a self-contained unit with a display and buttons on the front that allows the socket to be programmed etc. directly without having to use an app. I had forgotten about a device like that. A plug and play device like that can be useful as it needs very little set up for it to be used straight away. I have a similar type of very common plug and play device for measuring current and it can also be programmed as a timer etc.