Cliff the Z Man Zlotnick on IAQ Radio
If you suspect a dead animal hiding in your walls (because you're house smells like a dead animal), here's what Cliff the Z Man Zlotnick does, as described back in 2007 on the IAQ Radio Show:
Put a handful of raw ground beef in a garbage bag in a wastebasket and leave it outside. Within minutes, flies will be attracted to the meat. That's when you close up the garbage bag, bring it inside, open it back up, and watch as the flies fly straight to the problem. The gases that emit from a dead animal pass through the wall itself, and the flies can smell that.
Image credit: AI Art - Middle Aged Woman Using a Nebulizer - 2023
Mandatory shout out to Avery Gilbert and his I Smell Dead People Column on his First Nerve blog (or his newer substack).