When I was designing the downdraft for my plasma cutter I was concerned that it might eject too much metal dust out of my shop and into my driveway. It turns out that I was right and as I've been cutting more I've noticed a real uptick in accumulated metal on the ground. To address this problem I built a filtering system designed to remove the bigger particles from the exhaust. Since I'm not concerned with smoke and really extremely fine vapor I was able to make a "solid state" filter that takes advantage of the inability of a heavy particle to follow a tight corner. It was inspired by cyclonic seperators on larger shop vacuum systems. From the testing that I've done it seems to work quite well and I'm pretty happy with the results. Check out the video if you'd like to learn more.