Are You Breathing Dead Possum? — Crawl Spaces, HVAC, & IAQ
If you were a really strange person, or even a normal person who maybe just has some really odd ideas, and you wanted to breathe the gaseous emissions from a dead, rotten decaying possum, while in your home, how would you do it? I know what I'd do. I'd go get a dead, rotten decaying possum and put it right in my living room. That'd do the trick. And if I needed to turn it up a notch, I'd throw some more dead, rotten decaying possums on the pile.
The next best thing
The next best thing would be to keep the dead possum outside your home, say in the crawl space, and pipe the emissions into the house. That's exactly what these homeowners were doing, unintentionally. Our friends at E3 Innovate in Nashville, Tennessee sent us this photo of what they found in the crawl space under the home of one of their customers.
See the possum? See the problem? The dead possum by itself is bad enough, but there's one thing in this photo that makes it even worse. The photo below shows you what it is.
The possum that the guys at E3 Innovate found in this crawl space just happened to die right next to where that disconnected return duct was lying on the ground. What that means is that all those nasty emissions from the decaying possum corpse have an easy path into the house.
What about that return duct?
Now, if you know anything about forced air heating and cooling systems, you may be wondering what the other end of that return duct is connected to. It could be connected to a return grille, in which case the noxious emanations would travel up into the house relatively slowly. Anytime someone in the home walked by that grille, they'd get a powerful whiff.
The other possibility is that the other end of the disconnected return duct is connected to the air handler. If that were the case, that open duct lying there by the possum carcass would be pulling air strongly from the surrounding area whenever the heating or cooling system was running. That fetid crawl space air would then get distributed to every room in the house.
In fact, in this home, the latter was the case. The disconnected return was connected to the air handler. The owners knew there was a bad smell, but had no idea where it was coming from or why it was so bad.
The immediate fix here, of course, is to get rid of the dead possum and then reconnect that return duct. To solve the general problems of having a vented crawl space, encapsulating it is the ticket. E3 Innovate does a beautiful job encapsulating crawl spaces, which they did in this home. The photo below is from a different home, but you can see how nice it looks when it's all shiny and clean.
First of all, when you go to all this trouble to encapsulate a crawl space, it's a lot less likely that you're going to get possums in there. I'm not saying it'll never happen, but it's improbable. If one does get in there, it's pretty easy to find and remove.
This is why that old expression about possums is so popular. You know the one I'm talking about, right? The one about how something "stands out like a dead possum in an encapsulated crawl space." Surely you've heard it before.