Hi, I've never posted here before, but this question and response
(below) have my attention.

First, what is an ozone machine?  Second, my 15-yr old male cat has
taken to peeing all over our basement, which has carpet covering all but
the laundry room.  I'm buying one of those pee-detector-light gadgets to
see exactly where his pee-spots are.  I've found a few spots and have
sprayed an enzymatic cleaner, and washed the washable things, yet the
oder persists.

The thing is... why is he doing this?  He lost his best friend (a female
cat one year older) a few years ago, but came out of that sadness, put
weight back on, and has taken to the two kittens we brought home from
the shelter (both girls).  At first he hated them, but now they play and
sleep together, etc, so I don't think the girls are a threat.  I've
placed mothballs outside the windows that look into the basement to ward
off neighborhood cats... and still - the basement now smells pretty
horrid.  And we have 3 litterboxes, two downstairs (where the pee is!)
and one upstairs.  Oh, and he does not do this upstairs!

He has not tested positive for UTI in the last year, so I'm wondering if
this sort of thing can be behavioral...?  And then what to do?  If it
continues on and is untreatable by the vet (who we will see soon), I
fear we'll have to put him down -- we cannot live like this and he is
too old to suddenly become an outdoor cat.  Thoughts, suggestions, advice?

Thanks.