When dealing with any significant amount of urine, one must use more than simple ozone to remedy the problem. O3 is amazing but it is not Casper the Friendly Ghost, in other words it cannot pass through walls floors or solids objects. Urine however utilizes a scientific process called capillary action as it is made of water, to diffuse into porous substrates. When treating urine according to the IICRC Certified Odor Removal Technician Manual, it requires a 3 step process. First saturate the affected areas with white vinegar; the acetic acid will neutralize the alkali salts that are left behind as urine dries. Secondly spray 6-20% Hydrogen Peroxide, in suspect areas, to borrow the capillary capacity of the water component of the H2O2. This carry a free radical oxygen into the porous areas, and will crack the proteins. Lastly run the ozone generator. In rare cases if there were multiple male cats peeing over time a 12-18 inch flood cut of drywall may be required.
There you go, that is how to deal with urine, straight out of the IICRC.
In order to eliminate urine it must be addressed scientifically. Urine leaves the body as an acid, but then dries to an alkaline salt. In order to destroy it, first apply straight white vinegar to neutralize the alkaline salts, then saturate the area with 6% hydrogen peroxide to carry the free radical oxygen into the porous substrates. Finally apply high concentration ozone shock treatments. This recipe comes straight out of the IICRC Certified odor removal technician manual. It is often a good idea to use a black light to indicate the areas with urine. Sometimes with male cats you must cut the drywall up about 12 inches in extreme cases, in addition.