Oh dear god you boys ask me something like that. I don't use C02 because I grow w/animals in the room but have heard that you need some pretty high numbers for it to be worth using. i remember talking about it to my hydro guy and he said the numbers are high enough that you would not want to be in the room while you are using it due to lack of 02. There are some fairly inexpensive ways to do that. The only one I looked into at one point was something called ExcelloFizz that you add to water and it creates co2. dry ice is another method. Then there are the machines etc.... That is the extent of my knowledge on that.

For you fan....much more effective to pull hot air out than push cool air in if you go with one fan only. I have one for my reflector and it is on the exhaust side pulling rather than pushing. For my 1kw I have an inline 177cfm and it does the job beautifully. I can put my hand on the glass of the reflector while it is running.

When i first bought my light I needed the central a/c PLUS a room a/c to keep the temps down to livable (about a 12 x 16 room) and I kicked and screamed about adding a cooling fan. It has solved my problem completely and worth every penny. :thumbsup: