First and foremost any body fluid or contaminated material must be removed. Without doing that, the odor will continue to return. Any non-porous structural areas must be cleaned.
We typically use our ozone system which fills the room with pure ozone to oxidize bacteria and eliminate the dead animal odor in the room, by essentially eliminating all O2.
This process can take 24 hours, during which nobody can be in the residence. After, the odor should be gone and should not return.