Ceiling HEPA Filter FAQs

Ceiling HEPA Filter FAQs

Ceiling HEPA Filter FAQs

Used most commonly in cleanrooms, operating rooms, anterooms, and pharmacies ceiling HEPA filters come in many different styles.  This style of “cleanroom filters” are the most common and safest type of HEPA filter for operating rooms.  Across all of the options and all of the applications there are a few common questions that get asked regularly and we’ll answer them here.

Can I replace just the filter?


Not the answer you were looking for I’m guessing, but it depends on the housing.  If it is a room-side-replaceable (RSR) or bench-side-replaceable housing than yes you can, although with bench side housings it may be easier, less time consuming, and lower cost to just replace it all as you need to disconnect the housing from the ductwork anyway.  The answer gets less clear with Fan-powered units as the fans typically don’t last much longer than the filter so it depends on what is causing the need for a filter change as it may be more advisable to replace both the filter and housing to get a new fan too.  Some of the high-end fan-powered units have nicer ECM fans that will long outlast the filter making filter only replacement a viable option, but the initial cost of these units makes them rare.  If you need a quote on replacement HEPA filters, visit our HEPA Quote Page by clicking here.

Are there standard sizes?

No – not even a close.  Although the overall housing sizes of 2’ x 4’ and 2’ x 2’ are very common so they can fit easily into a drop-down style ceiling, the filters that go into those come in all sorts of sizes.  Part of this is because each manufacturer installs different options like service ports, injection ports, and damper adjustments in different places and different mechanisms there are a lot of other variables that make them different.

Do I have to replace if any leak is detected?

No, it is quite common for the filters to have or develop tiny pin-hole leaks.  In most applications it is permissible to “patch” the hole with an epoxy or other sealant.  You do however need to review any off-gassing concerns of the material used as a patch as the processes done in the space as it may be sensitive to some molecular compounds that are off-gassed (especially in microelectronics manufacturing facilities).

 Are all of these filters made from fragile Micro-glass/Fiberglass media?

Fiberglass is far and away the most common media, however there are some applications that cannot have some of the off-gassed molecular compounds the binders/glues used in that media emit.  This has caused manufacturers to make investments in developing ePTFE media filters, the first to use ePTFE was Camfil in 1993.  This media – typically referred to as membrane filters – is very durable and doesn’t off-gas like traditional fiberglass media.  However, ePTFE media typically won’t last as long as fiberglass because it doesn’t have the same dust holding capacity per square foot.  It also has a tendency to degrade in efficiency, largely because it gets eroded by PAO, which also increases testing/certification costs as PSL needs to be used so the filter isn’t prematurely damaged.

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Am I o.k. always using Tri-Ethylene Glycol as the challenge aerosol when testing/certifying?

Always is a dangerous term.  In most cases this challenge aerosol is fine, which is why it is the most commonly used.  It is also the aerosol used when factories use a visual scan method to test filters before they leave the factory.  In some cases it may be required that a PSL challenge is required.

Do I need to include a mixing box?

That really depends on the housing and manufacturer.  Typically if there is a diffusion disc or prefilter in the housing having a mixing box is redundant and not needed.  There are sometimes when it’s a good idea and should be handled on a case by case basis.

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