Nitrogen purity for exit bag method

[Fromama]

What is the optimal flow rate and bottom bag tightness for exit bag method, if my nitrogen purity is 97% ?
As I understand the flow rate - 15 liters per minute and exit bag - pretty tight, but to fit two fingers, but it is for high grade nitrogen 99.9% purity.

 

[FromGermany]

My dogs are waiting for me in the bedroom, but I saw this in the last moment by chance and will answer it correctly.

15 Liters/Minute is not enough. You need at least 20 Liter/Minute, regardless of the purity.
I would never play with purity. It's very important, what is in the remaining 3 %.
Nitrogen 2.8 is the minimum.
This 2-fingers-story is also not working in every case.
If one has fingers like a Gorilla, then the bottom of the bag is wide open.
A bag must still fit, if you shake your head like a maniac.
You can test it that way.

 

[Fromama]

Thanks.

Maybe someone else has advice?