Jun 6, 2017

Your dust collector is supposed to keep dust or fumes from getting back into your facility. That means that the last thing you want to see is what we found when our ServiceMAXX technicians went on a service call to this facility: badly leaking filters in their horizontal dust collector.

How do you know you have leaking filters? Obviously, you might see dust in places it shouldn’t be, like coming out clean air vents. You might also see dust in the clean air plenum of the collector, but this isn’t exactly a place that’s easy to get to, especially in a horizontal collector.

The best way to find out if you have dust getting through a leaking filter is to have a professional conduct a dye test. Not only will this show you whether there are holes in your filters, but it will also show you any other places that dust is getting where it shouldn’t be.



In a dye test, a dye that fluoresces under ultraviolet light is run through the collector just like regular dust. After this has been allowed to go through the collector, everything is inspected with the UV light.

If there are no problems, the dye should only appear on the outside of the filter: the side that is supposed to be in contact with dust.

When spots on the inside of the filter start to light up, you have a problem. Dust isn’t supposed to be on the clean air side of a filter, and if the dye is getting through, dust is too.



When our service technician visited this company, he found filters that looked like this:

Leaking Filters Dust Collector Filter

Leaking Filters around the edge of dust Collector

The blue marks show where the dye accumulated after running through the system. This allowed the service technician to discover the locations of several problems. Some of the filters had holes in the filter media, which was probably caused by large particles hitting the filters and damaging them.

Some of them also appeared to be leaking around the gaskets. This is a common problem in horizontal collectors because of the yokes that support the filters, which are easily bent. This can pull the filter away from the tube sheet or the door and cause leaking filters.

Leaking Filters Leaking around the gasket in the Dust Collector

This photo shows how much dust was sitting on the yokes. These are inside the filters and should never have any dust on them unless you have leaking filters.

Dust Collector Filter Yoke

Our technician then took a look inside the clean air plenum to see how much dust had been getting past the filters. The results weren’t good:

UV light revealing large amount of dust inside clean air plenum

This valve in the clean air plenum should have no dust on it or in it. The dye test showed a large amount of dust accumulating inside the clean air plenum. This dust can be very difficult to clean out, even after leaking filters have been replaced. If there is dust in the clean air side of the collector, it will continue to get into your clean air stream even after the filter issue is fixed.



Any system can benefit from inspection by a trained technician. This can find problems you didn’t know were there, or things that can be fixed to prevent a problem.

Some problems that may be identified by a dye test:

  • Defective filters with manufacturing flaws
  • Failure of gasket seals
  • Damage to filters due to large particles hitting them (or being handled incorrectly)
  • Filter material damaged by high differential pressure
  • A bent or warped tube sheet (usually a problem in horizontal collectors)
  • Other areas where dust is getting through
  • Dust in the clean air plenum from past leaks that needs to be cleaned up


One frequent cause of filter failure is using the wrong filter media for your dust. DeltaMAXX nanofiber filters are highly recommended over cheaper and less efficient material, and for special applications media like spunbond PTFE can be used. The wrong filter media can cause filters to fail very quickly.

DeltaMAXX Filters

As another good reason to have a technician pay a ServiceMAXX visit to your facility, the inspection and dye test results can be presented in a report to prove that your facility is in compliance and everything is up to standards.