It is risky letting unfiltered outside air into the grow room. Mainly BECAUSE of the risk of bugs.

However I've been doing it every morning to air out the room after having that Hotshots pest strip in there. Then once the stink goes away, I close the outside window and open the hall door to cool the room (I need a fan, filter and hoses to cool my new hood).

Sorry I can't help on the gnats. Haven't had that pleasure yet. It seems I've had all your other issues, as our grows progress too. SURE hope I don't have gnats too!:wtf:

Investigate how gnats handle the cold too! If they don't like it cool the room a LOT at night. but just an idea!