A homemade air quality sensor : is it viable?

The fact that indoor air quality is a very important topic has already been proven by Wybon back in 2014 [1]. Although more and more commercial sensors become available to start collecting your own data, these sensors often turn out to be very expensive due to mandatory services being involved. This project measures indoor air quality by means of a homemade sensor. Goal is to check whether it is viable to come up with your own IOT device and to use it for empirical research.