CATS and their URINE //
Since Scary Mary and her 5 kittens came around over a year ago some of my house cats, mostly Larry, have been spraying cat urine in the house. The urine can be smelled but hard to find. I bought some UV (Ultra Violet) LED Black light flashlights to pinpoint the areas.
They work very well, too well in fact. The UV light shows body fluids and proteins. The places a good housekeeper thought were clean.
Here are some tips in finding Cat Urine and a follow-up video, "Insider secrets for getting rid of cat pee smell." It is just under 10 minutes long but well worth sitting through if you have this problem.
FINDING CAT URINE
Get a good UV LED Blacklight flashlight, more LED's the better.
Use at night in darkness.
Search area that smells with a sweeping motion.
Mark with stick-ons or remember where stains are and clean.
Besides normal household cleaners, you can use enzymatic ones like Nature's Miracle that break down the urine and remove the smell.
Video to watch 
The little darling that likes to mark his territory.
Larry
Did not know a black-light flashlight existed; great info! I've only had one that marked in the house. Glad my 3 boys now don't do that. Have a big gallon of Nature's Miracle just in case; great stuff!
Going to have to get some. NM
Great post! I need one of these flashlights. Our bedroom smells of cat pee but I can never find it.
These were cheap both for $16. You only need the big one, comes with 3 aa batteries.
Very interesting the technique used to detect areas with smell of urine of cats ... every day, definitely, one learns new things ... ultraviolet light is the solution.
Thanks for the information and recommendation @ manorvillemike.
Greetings.
UV light saves time and sanity.