It shouldnt hurt them. I noticed last night that my timer that was set to 18/6 had been bumped or something cause it was on 23/1 and i dont know how long it was like that. Three or four days prob, if not longer. It didnt hurt mine any. Adding more ventilation wont hurt anything but as long as ur temps stay under 100 at plant height u should be ok, under 85 is better though. LMAO the cheapo fan from walmart and pc fans are what im using. The cheapo n the box and one 80mm exhaust and one 80mm intake, ducted and filtered. The 4? duct is only 3mm biger than those pc fans so it zipties on nicely :thumbsup: