Is it possible for a cat urine spray to have no odor? We have cat-butt high yellow areas on white curtains but there is no smell whatsoever

Cat sitting in windowsill might have peed on the curtains

If these stains are indeed cat urine, consider yourself lucky that you cannot smell it!

If the cat pee is very old and if you live in an area of year-round low humidity (or a home that is environmentally controlled to the same standards without fluctuation), it is possible that you will not smell the cat spray.

It is also possible that you are one of the few people who are physically incapable of detecting the odor of cat urine. To test this theory, you could have other people come to your home and have them smell around the stained area and tell them to tell you HONESTLY if they smell anything. To be sure, try moistening the area with a wet paper towel first (as humidity ‘reawakens’ the smell).

What will this gain you? Well, if it is cat pee and everyone else who visits your home can smell it (but you can’t, then you are doing yourself and your guests (as well as your cat!) a disservice by not cleaning it.You do not want to secretly be known as the “cat-pee house” do you? If you know that there is a problem, then you will be able to quickly, safely and effectively neutralize the odor for good by using an enzyme cleaner that is specially designed to eliminate cat urine.

What will this cost you? You’ll need a few “fresh noses” (best not to pick genetic relatives as they may not be able to smell the scent either) and be prepared for an honest response that you may not want to hear. Yes, you might feel embarrassed, but it is better to know now than later. The longer you wait to fix the problem, there is a possibility that the problem will get worse (either the smell will encourage your cat to continue spraying, or your household textiles may become permanently stained or bleached). The longer the problem sits around (or if it is ongoing and you do not realize it), your home could be incurring thousands of dollars worth of repairs (replacing carpet, underpadding, subflooring, baseboard, even drywall) or resale value. https://www.trulia.com/voices/Home_Buying/Is_it_insane_to_buy_a_rental_property_that_has_cat-356029

Whatever the cause, you will probably want to try to clean those curtains in case the stains are actually cat urine spray. To be safe, treat them with cat urine enzyme cleaner as directed. Then you may wish to soak them in a pre-treatment for organic stains, gently wash them in lukewarm water by hand in a large laundry tub (or bathtub), rinse well and allow to dry outdoors in the sun (UV light helps to whiten fabric).