I have been using a manual CO2 meter to read grow rooms and then on/off timers to adjust cycle times on negative pressure exhaust  for a couple of years. I have multiple grow rooms of 165 sqft.  I'm contemplating moving to CO2 controllers, primarily for greenhouses, and I see a few out there for under $150. Any preferences? Good experiences, bad experiences? 

I have one InkBird that I use primarily to exhaust the whole facility during closed up winter months.