If you are just running it to cool your lights, as a weird kind of closed system (weird because it's essentially open to the Great Outdoors on both ends lol), you don't have to worry about pathogens at all.
The air around your PLANTS should be exchanged from within the home, though, unless you plan to filter it.
stinkyattic Reviewed by stinkyattic on . ? about venting from crawlspace to attic If a person wanted to set up a 4' X 5' flowering room, using a 1000W HPS (w/ cooltube) would they be able to bring in "fresh" air from underneath the house, from the 2ft crawlspace, through the cool tube, and up to the attic? The reason I ask is b/c the air under most houses is kinda stale, but it is very cool, just wondering if you start moving the air if it would start becoming more "fresh". There is also concern with a little bit of moisture from under there, which they are trying to get Rating: 5