The actual MQTT payload seemed to have some sort of custom encryption on it (not the usual MQTT-over-TLS). I didn't dig deep enough to find out how it works, but it didn't seem very sophisticated.
Free big data for everyone.
The whole of Internet will know when you spoil the air :P
I know that you are joking, but the data from an air quality monitor can reveal a lot of useful things, such as when somebody is at home.