I am going to discuss a couple interesting facts that affect dog urine odor removal. First what I call Odor Memory. This is when we (humans) smell a particular odor and our brain remembers it. For example urine. If we smell urine and it gets into our nose and brain then certain things like seeing the urine stain again will trigger that smell in out brain and we will smell the urine again even if the smell is not still there. This is a psychological odor that is not a real odor but our brains can't tell the difference. Sometimes we can just think of the smell and we will smell it. It happens with all types of smells. Most of us have had this happen. This affects removing dog urine odor because we can psychologically smell the odor even after we have removed it. Sometime we wnat someone else to test smell the area we have cleaned to see if the odor is gone.
The other interesting point is that on average women can identify 10,000 distinct odors and the average man can identify 5,000 distinct odors. Thus women are more sensitive to odors than men. If you want a better test to see if the odor is removed have a women check it out.