Is a leakage rate of 11 ltr/min using a ResMed S10 Autoset excessive?

I am using a ResMed S10 Autoset with the new ResMed Airfit F20 full face mask. This mask is the best that I have ever used and I think that ResMed has hit a home run with this design. My wife and I both believe that this mask does not leak at all so I don't understand why I get a leak rate of around 11 liters per minute about every night. I read that ResMed subtracts the amount of air vented from the calculation so I don't understand why my reading is not ZERO. Anybody have any ideas about this?

The machine does subtract an amount from the leak rate which to allow for the intentional leak out of the exhalation port. However this amount is simply an arbitrary number which is preset in the software. Since you are using a ResMed mask is should be close-ish to correct but I don't know for sure. In short 11 is not a big leak rate, even on an AirSense. It is not enough to impair the function of the machine. If you are comfortable and your AHI is still low you don't need to worry about it.

I am very happy with the leak rate of around 11 as my readings have never been this good with other masks. I was just wondering why it wasn't lower if I didn't have any mask or mouth leaks. Thanks for your reply.

Probably just a silent leak that isn't bothering you.

My friend at work has the same set up as I do except his Airfit F20 mask has the foam seal instead of the flex seal that I have. He showed me his leak rates this afternoon and most of them were a 1. So, I guess it is possible to have a nearly no leak mask. I don't think that I will change seal types. I do like the one that I have been using for the past month. Thanks for your inputs.