[Ray Rogers]

I generally hear 100CFM as a desired minimum but many successful forges are built with less. Mine is 160CFM and is just barely enough for the bizarre burner set up that I created. One thing is for sure, it's difficult to have too much as you should always be able to turn it down. How much CFM your forge needs will partly depend on the volume of your forge body and your burner design. Smaller forges need less CFM.

CFM though is not the only measure you need to find an adequate blower. Many squirrel cage type blowers are just fans, they move 400 CFM of air perhaps but they will only do it if there is no back pressure. Blown forges have a good deal of back pressure so you need a blower that can push air against resistance. You rarely see them rated this way but those that are will say they provide 32 ounces of force or 40 ounces, etc. Those ratings are enough if you find one. So, look for blowers intended for forges like my commercial unit at $125 or look for one designed for pushing air like a vacuum cleaner, or a hand dryer, something like that. Those are almost certain to work but other less beefy blowers may also work depending on the details of your burner design.

Finally, don't be afraid to try any blower you can get. The worst that can happen is that it won't work well. If you can feel air coming through your unlit burner with a slight push against your hand you have at least a marginally workable blower. The more air you can move, the more gas you can burn, and the hotter your forge will be ...