Quote Originally Posted by dumass
Beyond the possible CO2 loss from having the exhaust below the house is the threat of alien invaders!
Well, where i come from the air is free including the 300ppm co2 it contains,And he's using his cellar or basement(I assume) for an intake,I told him to use a filter also,as long as the area below the house is vented(screened windows or air vents)he should have more than enough fresh air and co2 for a nice grow....bonbon