Okay, one day you get back from work and there is an off smell in your house. You walk around the house but you can’t identify where the smell is coming from. Then it hits you, literally, the smell is coming from the crawl space and you been fighting rats (or mice) for the last couple weeks with rat bait. Now you need to find the corpse and neutralize the smell. In most cases the dead rodent is going to be very difficult to find, usually hidden in the insulation, behind a wall or maybe if you are lucky, just sitting in the middle of the room. The smell from a dead rat usually will last for 4-5 weeks and a mouse for a couple weeks due to their body mass. The smell given off by the rodent’s body when it swells and exudes fluid can spread up to 300 meters away from the corpse. So let’s deal with the smell. Odor Eliminators are an effective bio-method that has an enzymatic component that eats the odour rather than trying to mask it. Organic products are available such as Ona Pro Gel and Rocco & Roxie’s Pet Stain & Odor Eliminator. Bagged absorbents such as Earth Care Odor Removing Bags are helpful when you know exactly where the rodent’s corpse is but for some reason you can’t actually remove the body; be it behind a wall or somewhere in a localized insulation area. Other absorbents such as charcoal and coffee grinds are a hit and miss. Air Ionizers and purifiers can be useful in combination with other products. Acetic acid, chlorine and formalin are considered to be professional disinfectants which are very effective products for getting rid of putrid smell. These products are for professionals as they are toxic and have a high risk of burning hazard.
http://www.delta-optimist.com/opinion/blogs/blog-my-house-smells-like-a-morgue-1.2364486