Many times I have mentioned that a simple VOC sensor isn’t enough to determinate if the air quality is good or not especially in interior environments. Formaldehyde CH2O is a VOC and since I have an AQ monitor uRAD A3 that features both a Formaldehyde sensor and a VOC sensor I will try to find out if there is a correlation between them.
I have been monitoring my house for Formaldehyde for over a month now by leaving the AQM on including while I was out on a trip for 4 days and during that time the house was well closed. This kind of experiment allowed me to determinate if my furniture, paint, etc outgassing Formaldehyde.
The measurements below were taken from 11-March to 15-March 2018. You can immediately notice that there isn’t any correlation whatsoever. Some spikes of CH2O (the blue line) were actually due to the wine I used during the cooking process. The alcohol can interference with the CH2O sensor.
There is some low concentration of CH2O in my house between 0 and 0.1ppm totally acceptable by me.
Interesting observation, there was some correlation between Formaldehyde and Carbon Dioxide CO2. As a result, remember to open your house windows if the outdoor conditions are good.
All in all, we can’t make assumptions about the indoor air quality just with a VOC sensor. VOC sensors are also vulnerable to interference by other gases in the atmosphere, so by having a narrow sensor that only measures one gas we can be more sure about the air quality.