# can we stand another dust collection question?



## Sawdust2012 (Sep 17, 2013)

I recently bought a used dust collector with a cannister filter. Maybe I was foolishly optimistic, but I expectied it to function correctly. When I fire it up, i sometimes see small whisps of dust blow out of the side. Today I noticed, when I turned the crank on top that small flecks of sawdust popped off the outside of the filter. My question: Do I need to replace this filter? If not, why is dust shooting out on start up? How do you know when one of these is shot?


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## gfadvm (Jan 13, 2011)

Sounds to me like you have some small holes in the filter 

If there are only a few, you might be able to patch em with epoxy, etc. Otherwise, it's new filter time.


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## crank49 (Apr 7, 2010)

I can't say for sure with out personally inspecting it, but it might be ok.

Starting with a perfectly clean filter, it is normal for a little dust to pass through a filter's media until a "dust cake" is formed. Well, unless you are talking HEPA filters. HEPA, High Efficiency Particle Arrestors, are designed to catch everything from the start, but most other filters depend on the dust cake to capture he finest stuff. However, after you have formed a thin layer of dust inside the filter you should see no more dust passing through untill you clean the cartridge again.

By now you may be wondering how often to clean the filter. The answer to that is when the pressure drop across the filter is so high the performance of the collector starts to degrade due to reduced air flow. You need a "U-tube" manometer to see what this pressure level is and then you can see at a glance when the unit needs cleaning. It is very simple to make one of these and you really need one if you are serious about dust collecting. You can look it up on Google or Youtube faster than I can describe it.


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