Odd Low Level Leak

[richcrab]

Hi all. I recently replaced my three month old AirFit P10 with a new mask (thank you insurance); same size same model. However, I am finding a constant leak rate. For example, with my old mask I might have long periods of no leakage registering, interrupted by an occasional spike or two. With the new mask, I get a constant baseline leak around 2.0-3.0 and spikes occur off that baseline. That is not the way it looked under the old mask.

To me, it seems to suggest some sort of ongoing and oddly constant leak at a low level. I've attached a JPG to show this.

Any ideas? Thanks.

[AlanE]

Compared to mine, your leak rate is very low. Mine hovers around 25 all night.

[Sleeprider]

Maybe they have redesigned the exhaust diffuser mesh a bit. There were complaints it was not flowing freely after washing. I don't know if that was true or not, but several threads dealt with that. A slightly freer flow might show up as a low-level leak in comparison.

[Rcgop]

Yep, it's the mask. Same thing happened to me. My first mask started at 2.0 until I got my first replacement. My new mask started at 0 unless I had a real leak. It was very plain this was happening because the day I changed to my new mask I had taken a nap with the old mask. You could see the difference in the two sessions. For a test, several days later, I changed back and the 2 liters per min leak came back. I tryed cleaning the old mask with no change. I can't say this a defect or not, or will change anything, but it is very real.

[justMongo]

I suspect it's an artifact of the calculation of leak rate.

The machine has to find the baseline for the absolute flow from the machine; I assume by numerical integration of the flow waveform.
Then subtract a mask vent rate at the measured pressure -- probably a table lookup.
The difference is the calculated leak rate.

If they did increase the vent rate, it wouldn't match the table; and the resulting leak rate would be calculated as higher.
Following that logic, it's the mask...

[richcrab]

Thanks of the thoughts everyone. So is the point here that the new mask is more or less the same as the old mask (which it should be), but that the leak calculation is starting from a different baseline? Or is the point that there is some sort of constant leak or maybe even defect in the new mask, and it should be addressed? Sorry, it wasn't entirely clear to me. Thanks.

[justMongo]

I'm thinking they increased the vent rate of the mask. That tricks the machine into thinking there is a 2 LPM unintended leak.