Shaker Felt Filter Bags for Dust Collectors

I just bought a pair of your Shaker Felt micron filter bags for my DC101 2HP dust collector. Now that I've got them installed, there seems to be something wrong with the machine. Though the noise it makes sounds normal, it doesn't seem to be working right. The bags don't influate at all—they just hang there as if no air is getting to them. What gives?

Welcome to the world of high efficiency filtration, pardner. There's nothing wrong with your dust collector, it's just that for the first time there's nothing wrong with your filter bags, either. It seems close to miraculous: our new micron bags capture particles up to 100 times finer than the bags that came with the machine, but they allow air to pass through far more readily, so easily that you can blow 1200 CFM through them without even noticing. It's not hard to imagine that your collector must be working far more efficiently than it did when the filter bags were rigid with back pressure. As you use your Shaker Felt bags, they'll gradually load with dust and begin to show a bit more back pressure themselves—and they'll also filter smaller particles even better than when new. Shake them occasionally to knock off excessive "cake" on the inside, and launder them very occasionally to keep them working at their best.

One of the micron bags I bought from you appears to be defective. When sunlight comes in through the shop window across the dust collector, I see dust like smoke coming from the bag. I thought these bags were supposed to filter everything!

Brand new Shaker Felt bags are rated to capture particles down to around 3 microns in diameter (a micron is a millionth of a meter, quite microscopic). The particles in cigarette smoke, for comparison, are around 5 microns in diameter—so it shouldn't be surprising to see a thin, smoky haze of extremely fine dust making its way through the felted polyester material in a new bag. As a layer of dust builds up on the inner surface of the bag, it acts like a filter itself, ultimately capturing particles as fine as .1 microns. The more you use the bag, the better it works, up to a point. As the dust cake builds up inside the bag, back pressure increases steadily until your dust collector's efficiency begins to suffer. When your filter bags are very firm to the touch while the collector's running, it's time to turn off the machine and give them a shake to knock loose most of the cake. When you restart, you'll see a brief burst of dust coming through the fabric, but it will only last a moment or two. Experimentation will lead you toward a happy medium between cleaning too frequently or allowing too much back pressure to build up.