For those of you who are talking about exhaust. Please do not waste your money at Home Depot. They might have some panasonic whisper fans, and they are good if stealth is mandatory, but you wont get the better fans that dont require stealth.
Centrifugal fans for pulling air through carbon filters. Axial Fans for cool-tube, or air cooled hoods. Do not mix an Axial fan & carbon filter.
Ive used the crappy fans HD/Lowes has, and they dont cut it. Once you use a centrifugal fan or axial fan in the right way, you'll never want anything else.
Unfortunately, you either have to pay out the ass at a hydro shop locally, or search around on the web. Its best not to skimp on the key items, as you will realize after your first grow, that you needed more.