Intake and exhaust with CO2

I am about to make my grow room airtight so I can use CO2. The lights (2 600W HPS) I'm using will be aircooled with less than 10 feet of venting from start to finish. I assume its best to have the pressure in the room be a little bit positive so that I don't suck the CO2 out through any leaks in the lights/ducting. Am I better off using two smaller fans (one for intake and one slightly smaller for exhaust) or just one big intake fan? Thanks for any advice you can offer.

One big fan will do. Also, you don't want to pressurize the room. You want to pressurize the hoods and duct work if your concerned about pulling CO2 and odour out of the room.

redi jedi said:

One big fan will do. Also, you don't want to pressurize the room. You want to pressurize the hoods and duct work if your concerned about pulling CO2 and odour out of the room.

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Well I can see that at least my hoods aren't 100% airtight. So I can't really air cool the lights without changing the pressure in the room a little bit. If I was just using say a 300CFM fan pushing air through my leaking lights wouldn't that increase pressure in the airtight room? I'm a noob to venting and I'm pretty , but it seems like it might be a good idea to have an exhaust fan too to avoid any pressure issues. Does that make sense?

Not really...If your room was 100% airtight, the leakage from the hoods would gradually pressurize it but I very highly doubt that is the case. So don't worry about a bit of leakage. Adding an exhaust fan to create negative pressure is really a waste of cash...you can't run the fan while your injecting CO2 and you would need to add a carbon filter.

IMO, just cool your lights and forget about setting up another fan for ventilation.