Dodo,

I almost forgot, here is a link to the least expensive meter I have found
for mesuring CO2 in PPMs.

I use the TIM8 in my basement set-up. The PCB one is very interesting.

CO2 Meter - Best-sellers products
oldmac Reviewed by oldmac on . CO2 Safety and setup I'm in the process of setting up my grow room and recently purchased a controller that handles CO2. Yay me. I'm also at a point where I'm ready to cut the holes for my passive air intake and had some questions related to safety as I understand that when CO2 levels reach 5000 ppm they can be deadly to humans. Some background: My grow room is basically a full-size closet situated in a room of my house. Because of this setup I'm using the air within this common room to provide fresh air to the Rating: 5