the course of a day.
a popular method to remove odor from a mattress is to sprinkle baking soda on it. use as much as you want, and make sure to evenly distribute it over the entire top surface of the mattress. let it sit for a day, and if you can, open the curtains to let some direct sunlight help the baking soda work its magic. then in the evening, vacuum it up.
lots of people swear by corn starch as a means to clean urine from a mattress, including its smell. simply sprinkle the cornstarch over the spot where the accident occurred, and top it off with a few drops 