Question about lights and carbon filter

Hey I have a couple of quick questions.

Im building my own carbon filter and I'm wondering is it better to push or pull the air through the filter?

I'm going to use 250 watt HPS lights, how close can they be to the top of my plants?

For my ventilation how many times should my fans circulate the air in my grow room in a minute?

Could I get my lights at a gardening center?

And, How much should I expect the one light to increase my electricity bill?

anyone know anything?

hey bud im some what in your shoes, i got a small space about 5' wide 5' tall and 20 inches deep, im goin with T5's 3' 6 lamp then 2 single T5's on the side...though some one told me to use HPS, too much heat in my opinion, as for an exhaust fan im goin with a small 180cfm with a speed variator so the fan wont be on full power all the time, (probably never) but, as for a wall fan, im planning on a small 12 inch at max im sure a 10 inch would be perfect for my set up. carbon filter ill be using is the Eco Plus 4", thats plenty for my set up and an ionic brease just in case any small amount of air gets out of the grow room. you goin with dirt or hydro? if you need some sites for reference send me a message. im not saying im a pro or even a novice, just done some research with questions and answers... also before you grow, grab a book man. i ordered "Cannabis Cultivation: A Complete Grower's Guide by Mel Thomas" havent gotten it yet but i was lookin at it at Borders, gots alot of info in it.... Hope this helps bud. {Gasper}

from what i have heard when it comes to airflow,
its always better to pull than to push