It's a must,you can put the light closer to the plants and get fatter nugs+lower room temps,I have tried using 1 inline fan hooked up to the hood and filter which works decently in winter but not so good in summer since the room usually is warm.....I get better results with pulling air from the outside for the hood..... that way is more efficient for cooling...plus won't suck out Co2........if you use Co2...I use a separate inline fan+carbon filter and circulate the air in the room for odor control