you can get a 4" inline fan from Home Depot for about 20 bucks and it sits right next to 4" duct work in there heating isle, can regulate speed with a dimmer switch same as done in the DIY dryer box
tinytoon Reviewed by tinytoon on . Microwave Fan for Exhaust? We had a microwave that died a few years ago, and today I decided to experiment. I pulled out the fan, connected the two wires coming out of it to an old lamp cord, plugged it in, and voila, it works! I've been looking for a cheap exhaust fan for my grow cabinet (4'H x 2.5'W x 2'D) and I'm wondering if this just might work. The fan blade is only 4.5" across, but the whole thing must weigh close to 2 pounds. It blows like a mini-jet propeller, and from googling the CFM of microwave fans, Rating: 5