Double up disposable filter?

Happy holidays,

I have a Resmed S8 Autoset II. When I got replacement disposable air filters for the machine, my DME gave me non-OEM filters.

Would it work to put in two filters or would there be a danger of causing too much obstruction and limiting the the air intake of the machine? I don't want to damage the machine obviously but was wondering if two filters would provide twice the filtering of one?

Thoughts?

Also, I read a thread on the forum a while ago with someone writing they took a N95 face mask and cut it up to make their own HEPA-type filter for their cpap. Has anyone else tried this? Is it effective? It sounds like a neat idea to reduce allergens/dust and improve the air.

Thanks!

Hi - don't double up the air filters. I rang Resmed support to inquire about a noise in my S8 II on the finish of exhalation and actually got through to an engineer who'd designed some of the aspects of the S8 and S9 fans (close to xmas and he must've drawn the short straw). Anyway, I asked him about doubling the filters to reduce the noise from the fan, and his reply was unambiguous - 'No, don't double the filters. This would impede air flow."

We also spoke about the 'chirping' noise on exhalation. I said I figured it wasn't a bearing problem, since the noise would be constant, and the noise existed when I removed EPR, which would indicate it's not that. He agreed and we spoke for a few minutes. The jist of what he said (I'm not an engineer, just a failed physicist) was that they'd taken extra pains to ensure the double fans were as quiet as humanly possible, but that variables like how you breath, how your mask sits, tube length etc. meant the calculation of how the flows on exhalation (its turbulence) inside the chamber make it very difficult to design something that would be silent on exhalation. He did say on EPR the fan/s change rotational velocity, which again effects the air flow and which, while designed to be as mechanically quiet as possible, could cause some noise. He mentioned small things like the elbow joint on the mask may change the dynamics enough and sent me the old 'two piece' elbow joint for the Activa instead of the one piece, and asked me to try it to see how it worked. Sadly, it didn't, but I did notice if the chirping sound diminished the higher the pressure (and presumably the faster the fans turn), so it may be slow-fan==squeaky on exhalation; fast-fan not squeaky.

Anyway - DON'T double the air-filters. And as long as the OEM air-filter complies with the specification (and presumably they do otherwise the CPAP/DME wouldn't sell them), then they should be OK.