AirGradient Forum

VOC monitoring accuracy, setup and calibration question

#1

Hello.

I am inserted in buying the indoor monitor and wanted to get some feedback from people that already have one, please.

I live in a high rise and I need to monitor the VOC and PM levels for extremely sensitive occupants living with me whose health is affected by poor air quality.

I currently have 3 airthings air quality monitors and find that while they can be generally reliable for 70% of the time the 30% that they are not is so frustrating due to extreme fluctuations, no re-calibration options.

Some questions please,

  1. how accurate is the VOC and PM?
  2. is the indoor monitor easy to setup? I usually only use apps to run smart devices
  3. what about re-calibration? Can they be re-calibrated and how?
  4. is the connection to these safe? Does it show on public bluetooth or wifi?
  5. will this ship to Canada?

If there is anything else I should know? Any reason this won’t help me or be suitable for my needs?

Thank you

#2
  1. The PM levels are accurate and tested by AirGradient. They offer their own calibration/correction values, as well as EPA researched corrections. VOC, lets talk about that later
  2. Easy to setup. You’ll power up the device (you need to provide the wall adapter to USB) and then connect your phone to the new wifi name that appears. Then you’ll go to a page to enter your permanent wifi information. After that you can use the QR code on the back of the sensor to add it to the AirGradient dashboard. It is a website you can access from your phone and can save as a shortcut so it acts similarly to an app
  3. No recalibration needed for the PM sensor. The CO2 sensor does a self calibration every 7 days or you can initiate it manually if needed. It expects that sometime over those 7 days your location gets down to base level CO2 concentrations.
  4. Connection to the servers is using a secure HTTPS connection. No bluetooth presented and it’s personal wifi access point is only visible during setup
  5. I can’t speak to shipping to Canada, but I assume it would.

The VOC sensor is a “digital nose” in that it doesn’t show an absolute value of VOCs, but it shows an Index. When you first boot up the device, it will show a VOC level of 100 which is the base. If it goes higher (up to 500) then VOC levels are increasing. If it goes down, they are decreasing. This baseline level resets every 12 hours by default, so if you are monitoring long term events, such as painting a room, then this index will be of limited use to tell when it is “back to normal” but would show if it is getting better.

From the Dashboard site:

Since low-cost monitors like the SGP41 can’t measure exact concentrations, the monitor uses a relative index. VOCs are displayed on a 0-500 scale, with 100 as the baseline, and NOx on a 1-500 scale, with 1 as the baseline. You can adjust how often the baseline is updated to reflect the average exposure over a specific period. For example, setting it to 12 hours will show the air quality relative to the past 12 hours. For longer-term comparisons, you can increase the duration.

How do you know that the Airthings are not reliable for the 30% of the time? That might better help to understand if AirGradient will be an improvement.