Cat urine contains an odor producing protein that makes the smell super strong and difficult to eliminate, keep in mind spraying (marking territory, both male and females do it) has the same protein in higher concentrations. When cat urine dries it forms crystals these crystals are what makes its removal so difficult, regular cleaning agents do not eliminate these crystals, sometimes other cleaning processes push them deeper into carpets and/or wood. Later under moist conditions these crystals reactivate producing the cat urine odor again and again.
This is how you get rid of Cat Urine Smell
To completely remove cat odors you need a two step approach. You need to remove the odor producing urine crystals and then remove the odor that is imbedded to all porous surfaces. Keep your cat away during these processes.
f. Leave the room for 12 to 36 hours, depending on the severity of the problem at hand.
Upon return the room will have a chemical cleaning product smell (some people describe it as walking in to an indoor pool, others as a hospital smell) the odor will completely subside after 24hrs to 48hrs leaving no residue or perfumes behind.
Spraying Foot note Some Vets suggest that cats mark their territory, both males and females in heat, this marking is also known as spraying. Spraying is usually done on Vertical surfaces such as furniture and walls, it has a more severe odor than urine but same chemical composition, follow the same instructions as above.