It was faint at first. I’d catch a whiff of something easily off-putting, however then it would fade. I thought there may have been something stuck in the garbage disposal. I kept splitting up lemons & putting them down the disposal thinking it would do the trick. It didn’t. I was lighting scented candles & leaving windows open, to no avail. I simply couldn’t figure out where the smell was coming from. It was stronger in some rooms than others however it was spreading throughout the house. When I observed the animal pawing at an air vent, the light finished making on over my head. I got on my hands & knees for a close sniff at the vents. That’s when I knew something had died in the air duct, however judging from the cat’s reaction to the smell, I figured it was a mouse, however knowing there was a dead animal in my heating & cooling ducts was a frightening thought. I had to get the little guy removed & whatever parts of my Heating, Ventilation, & A/C system it had touched, thoroughly cleaned. Some Heating, Ventilation, & A/C companies told me to call animal control first to remove the mouse. I didn’t have the patience for that. I finally found an Heating, Ventilation, & A/C business who agreed to remove the rodent. Turns out it was an unfortunate chipmunk that caused the foul smell the air handler had spread throughout my home. The Heating, Ventilation, & A/C business removed the carcass, cleaned the space of ductwork where the chipmunk died & changed out the filter for the gas furnace & A/C. He ran a check on the entire heating & cooling system then commanded I consider adding an media whole-home air purifier to help with animal dander. I decided to go for it. I only want wash air inside my home from now on.