This may be a silly question, but I have no experience with proper dust collectors/shop vacs.

Do shop vacs/dust collectors, when operating, eject much air? I ask as I have a super cheap wet/dry vaccuum, that has a blower feature; and when I turn the vac on, it instantly begins both sucking and blowing simultaneously. I find this... annoying as it starts blowing crap everywhere that I would like to not be blown around!

I've been working in my garden for a while but I'm getting a proper workshop shed soon so will definitely not want things blowing around!

1 Answer 1


Do proper shop vacs/dust collectors eject much air?

Yes. All the air that a dust collector or shop vac sucks in, which is a lot, has to come out somewhere.

Exactly how the air is returned varies. Dust collectors generally return the air through some sort of filter that's much larger than the 4" or 6" intake, so the output is diffused quite a lot -- there's no blast of air from an exhaust port.

Some shop vacs also diffuse the exhaust so that there's no blast of air, but others send the air out an exhaust port. That's supposed to be a feature, as you can use the machine either to suck up debris or to blow it away. If it bothers you, I think you've got two options:

  1. Buy a different shop vac that does a better job diffusing the outgoing air.

  2. Make or buy a diffuser that you can add to the vac you have. It wouldn't take much to break up the stream of air so that it's no longer blowing things around.

Here's a diffuser from Craftsman that would probably work on any vac with a 2 1/2" output port:


  • Amazing! Yes, the vac I have at the moment is super cheap and has the same size in/out port. It doesn't actually have a proper filter inside, so it does throw a bit of sawdust from time to time - Fire hazard, I know, but I've been outside so far :D. The craftsman diffuser looks interesting, and I know I can definitely build some sort of removable baffle myself - An intricate maze inside of a plywood/mdf box should do the trick. It might actually sound like some high-end speakers at that rate.
    – physicsboy
    Apr 19, 2022 at 10:51
  • Or @physicsboy, feed the output port into another $10 "5-gallon pail cyclone collector" gizmo. Direct the high-speed blast into the bucket, let it out through a much larger opening where it will come out slower and you can direct it as you desire. With the price of lumber at the moment, almost any amount of plumbing parts will be cheaper than plywood.
    – FreeMan
    Apr 19, 2022 at 14:50
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    @physicsboy You should put a filter in your shop vac; without it, any output diffuser will just get clogged up. More importantly, it’s probably increasing the amount of fine dust in the air — you’d might actually be better off not using the unit at all. If it’s designed to take a filter, add one; if it’s not, toss it and at least buy one that does have a filter, or else buy a dust collector.
    – Caleb
    Apr 19, 2022 at 14:55
  • @Caleb Yes, I get you completely. I have been fine for the past few years and I've only been doing work outdoors when the weather allows. The issue I have with my crap, cheap vac is that when I add a bag on it, the suction decreases significantly :-( So I've been using it bagless, but it doesn't have a filter around the mechanism other than a crap foam thing with a float valve.... Might see if I can screw a filter or something to it to do a makeshift thing. Or try and put a Henry filter or something over it for fun.
    – physicsboy
    Apr 19, 2022 at 14:59

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