OSITO Oxygen Concentrator 1-7L/min Adjustable , 24h Continuous Flow ,90% Purity ,Low Noise ≤45dB SYK-608

I have a unit that is almost a year old. Recently it made a grinding noise and now the O2 output blows so much air it whistles!
The l/h does nothing to change it. I have left you two messages with my contact information.
PLEASE CONTACT ME!

I am very happy with this product. I am breathing and sleeping better.

OSITO Oxygen Concentrator 1-7L/min Adjustable , 24h Continuous Flow ,90% Purity ,Low Noise ≤45dB SYK-608

You do not indicate the oxygen% drops with increase in cfm. This not truthfull when all you say is 90%

Works great so far and is pretty quiet. Only thing is the water tank is pretty small. What i did is just added a bigger water reservoir on my wall and just don't put water in the small built-in tank. Works great and lasts for days without refilling. Definitely worth the purchase.