Elvis N.
I own 2 VP-1s
I own 2 VP-1s; 1 VH-1; and two VH-3s. The value for the price was initially excellent. But after a few months the VP-1 started beeping, meaning "low concentration". I cleaned everything, still beeps. I switched to new tubing, still beeps. There is nothing wrong with the air flow, but it still beeps. So the good investment is now a waste of $600. I tried the customer service phone but mailbox is full. I filled out the service form yesterday, no response so far.

