Larger better filter?

Here's a likely crazy thing I did today with my AirSense 10, which I do not recommend anyone else does, but here are the details if you want. Also tell me why this may be a terrible idea.

Parts that I ended up using:

• Stainless Steel Round Tube 13mm OD 0.5mm Wall Thickness (cut to about 3.5")
  Silicone Tube 1/2"(12mm) ID 9/16"(14mm) OD (only a short segment)
  Aozita brand 18/8 Stainless Steel Spice Funnel (just happens to be ~4" dia on one end and about the right diameter for CPAP tubes on the other)
  POWERTEC 70132 14-Inch Table Saw Dust Hood
  Filtrete 14x14x1 AC Furnace Air Filter, MERV 13, MPR 1900, Premium Allergen, Bacteria&Virus Filter
  CPAP Tubing Connector (connects one standard CPAP tube to another, for instance if you want to have a longer hose)
  Old but never used CPAP hose

In the era of smoke and pollen and COVID and other viruses I currently live in, I wondered if I could come up with a better filter solution for my CPAP. The filter it comes does little beyond keep dust out of the machine, and doesn't have enough surface area to be significantly improved without making the CPAP motor work too hard. So if I wanted a better filter, I needed to figure out how to have a larger filter.

This rattled around in my head for quite a while and mostly I couldn't think of a good way to hold a large filter until I recently saw the "Table Saw Dust Hood" above. So then I started ordering lots of little parts off Amazon to put it all together. Starting at the filter end:

• Duct tape the funnel to the dust hood. Make sure to get the duct tape tight at the lip of the funnel to get a good seal.
  Duct tape the furnace filter (or better filter if you can find one) to the dust hood. Now you have more than 200x as much surface area to pull air in through. Probably easier on the CPAP motor than the stock filter. Now your air filter to CPAP tube adapter is complete!
  On the CPAP end, if you open and carefully remove the filter door, a 13mm OD tube just fits, and you can insert it quite a ways. I watched a YouTube video on disassembling the unit to make sure this would not run into anything. I cut the tube about 3.5" long I think? The pipe cutter I used dented/curved the tube in at the cut, and I sanded and smoothed it further after the cut for a very smooth end which helps with pushing it in.
  Standard CPAP tube to CPAP tube (22mm OD?) adapters seem to all have 15mm IDs. I tried a couple things to allow me to mate that to the 13mm stainless steel tube, the silicon tubing happened to work perfectly and makes a good seal. Now your CPAP tube to Airsense 10 adapter is complete!

If I could find a place to get a wider tube for the intake I'd do that. Or maybe I'll use an old heated oxy tube. But I don't see any sign of pressure drop in the fairly flimsy tube I used, I don't think there's much of any resistance pulling in the air it needs through this giant filter. Going down to a 12" x 12" size filter would probably still be overkill, the dust hood also comes in that size.

Pictures:

Dust hood, completed CPAP machine intake adapter, assistant. Funnel attached to dust hood. I tightly wound much more duct tape after this. As long as it's tight on the rim of the funnel and the hood, it should be a good seal. Furnace filter taped on. Not sure how often I'll need to swap out filters. That seems to be the file limit, I'll add more in the comments.

Closeup of the CPAP end adapter (stainless steel tube, silicon tube over, inserted into CPAP tube to tube adapter): Inserted into the machine (with hose cover because given enough time one of my cats will bite the tube just to see what happens): All together now:

I designed a simpler option that uses any 3M respirator filter including N95.

viewtopic/t188649/N95-filter-for-Remed-Airsense-10.html

If you don't have a 3d printer there are lots of online 3d print services that print and courier parts to you. Like PCBway.

That’s nice! If I’d seen that I would have done that instead, I already have extra filters around.

This thread has officially been submitted in contention for this week's Rube Goldberg award.

m421 wrote: ↑

Fri Sep 20, 2024 11:58 pm

That’s nice! If I’d seen that I would have done that instead, I already have extra filters around.

Thanks, it's working really well for me.

Like you I was thinking there had to be a better filter option than the one that's on the machine and wanted to make sure that the solution didn't restrict airflow in and risk loading the fan motor. A pair of 3M filters have a large surface area as draw air in both sides of each filter, probably similar surface area to your solution.

While your new filter system will certainly flow better, what is the micron rating of this filter? What is the micron rating of the stock filter?

I don't know either...

Conrad wrote: ↑

Mon Sep 23, 2024 6:50 am

While your new filter system will certainly flow better, what is the micron rating of this filter? What is the micron rating of the stock filter?

I don't know either...

https://ap.resmed.com/knowledge/air_filter

Standard air filter:

Material: Polyester non woven fibre.
Efficiency: >75% for ∼7 micron dust.

Hypoallergenic air filter:

Material: Acrylic and polypropylene fibres in a polypropylene carrier
Efficiency: >98% for ∼7 to 8 micron dust. Efficiency: >80% for ∼0.5 micron dust.

Do you have this rigged for the other 17 hours per day that you breathe?

Conrad wrote: ↑

Mon Sep 23, 2024 6:50 am

While your new filter system will certainly flow better, what is the micron rating of this filter? What is the micron rating of the stock filter?

I don't know either...

I do know actually? Your choice of what filter to choose to put on this. That’s the point, with the much larger surface area you have a lot of choices up to and including HEPA filters.

ChicagoGranny wrote: ↑

Tue Sep 24, 2024 2:31 pm

Do you have this rigged for the other 17 hours per day that you breathe?

Yes. Thanks for your concern?

m421 wrote: ↑

Tue Sep 24, 2024 10:04 pm

Yes.

Wonderful