If you haven’t smelled the rancid odor of a dead rat, then consider yourself lucky. You will never forget it or the saturated stench that lingers in a house. The smell comes from a mixture of methane, sulfur dioxide, hydrocarbons and other chemicals that emanate from the decomposing rat body. The most effective way to eliminate the smell is to find and dispose of the body, then disinfect the area. BUT, if you can not find the dead body – the source of the putrefying odor, then how do you get rid of the smell. The truth is you really can’t get rid of the smell until the rat body has finished decomposing, which can be 3-5 weeks depending on the location of the deceased. You can mask the smell with vinegar, ground coffee, baking soda in water, or use a product called Ona which is an odor-neutralizing product.
https://gogreenpestcontrol.ca/what-is-that-smell-a-dead-rat/
https://www.linkedin.com/pulse/what-smell-dead-rat-randy-bilesky/?published=t