The best way to get rid of human urine smell is to mix solution of 50/50 ammonia and h2o. Spray it on the mattress and close the door and open the window. The solution somehow removes that smell but initially the smell of the solution is very strong so do it after everybody leaves for the day or when the room doesn't need to be occupied for at least 3 hours. :)
By
08/13/2010
I hate to say this but buy a new mattress and enclose it with a waterproof zipped cover. This will prevent it from having urine on it again. I think your old mattress will always smell no matter what you do to it.