S.R.
I scoop every time they go....use scoopable litter....then put scoops in garage or outside trash. that's the only way to get rid of the smell. The cat may also have gone on carpet?
My house didn't smell at all, but I would confine the cat when I wasn't home in a room with the litter and no carpet. It's a tough problem, but the only way to fix it is to basically follow the cat when they go and scoop immediately.