This was a very important milestone in the project.

Having just one sensor connected to the hub would not provide accurate readings. By the time the CO2 reaches that sensor, the concentration would be too high. 

The concept revolves around having anything from two to six small, wireless sensors scattered around an area, that send signals to the main hub every few minutes (5-10). When the CO2 averages are too high, the Hub detects that and starts the fan. Bluetooth does the trick as the distances are of a few meters only. 

Wero had some problems with the Bluetooth communication but he worked his magic. To the right we see the data that is being sent from the node, and to the left, the hub is receiving it. Great success!