I've found evidence of accidents on the carpet that I think are pretty old. Molly (almost 2 yrs) has been given free rein of the house for quite a while now, and I haven't caught her peeing on the carpet in several months (pooping is another story, but easier to clean).
For new accidents I've always used Petzyme and it has worked wonderfully. Then I happened to find one older accident, then used the blacklight to see evidence of others.
I tried Petzyme on the old spots and it might have taken some of the odor away, but not all. I then tried my green machine with the Pet Odor solution and I still smell it.
Any other suggestions?
Carla