guys thanks for ur replys.. but would i even get away with leavin my tent partly open durin lights off with the carbonfilter extractin the air and smell out.. that way air can get in the tent no extra fan needed??? i will leave my fan inside the tent on and i could hang another sheet of maylar where ive left part of the tent open as to block any light and air can come thru good idea?? coz to be honest i have the fan inside my tent i will have the extrater fan on the carbon filter and another fan would do my head in as the tents in my bed room .. or i could run the filter only during lights on with tent slightly open as normal then tuen carbon filter off at night close tent and hope the smells not to bad