closet + 400W HPS

what is the best(ECONOMIC) ventilation system for wooden closet90cx90cx2m and no?i will use 400w HPS for flowering.Seek always the most economical solution..

Just a word of warning mate. 400w HPS in a closet is going to give you temperature problems. Been there done that. Your going to need an extractor fan running full blast just to keep it cool. Especially if your venting back into the closet. That exhaust fan is going to sound like a jet engine running that speed. The sound problem is why i had to switch from 400W hps cooltube to LED's. Heat and noise are going to be issues for you.

i c .i hate sounds wen i m sleeping.thinkinh serius t use hight watage cfls for flowering 2 x 250w pehaps.thank y.

A 400 in a closet isn't a grow chamber, it's a large sized easy bake oven

I would suggest that you use a 440 cfm blower and vet the air out of a window if possible. I am running a 600 watt light and I have the temp in my tent to a 75 to 80 degree max and it only gets to 80 after the light has been on for about 9 hours. I will have better temp control when I can use my air conditioning but it;s like freezing here in MIchigan..lol

Magic Seth...if your blowing in cold air from the outside, just hook your fan to a temperature controller switch...done and done. Caution, and duct work you have going from window to grow space will get soaking wet.