Rotten Egg Smell in cabin

[passta]

15' M5 DCT. I've got a sporadic rotten egg smell in the cabin when running the AC. I'm not 100% sure this is related but here's what has happened recently. The blower housing for the blower motor has, or in my case, a foam filter on it designed to keep debris, leaves, and stuff out of the actual blower motor. They deteriorate over time, mine did sometime this spring, and a leaf got into the squirrel cage for the blower motor, making it sound like a 747 spinning up when running the AC. Saw it was an easy fix to pull the part out and fashion a replacement filter out of some foam filter of the same thickness and type I ordered online. Worked great, except car smelled like rotten eggs, but this was also right around the time it got hot enough where I live to really use the AC for the first time since winter so not sure if the timing of that is related or not. When I looked at the filter I ordered to fix it, I got charcoal-activated foam by mistake, so I thought that was possibly the cause of the smell, so figured it would just go away after a few weeks from reading about charcoal filters, but it has not, so I ordered the actual replacement part, was about $50 and came with the filter already on the housing, OEM part. Replaced the part, and the car still stinks, sporadically, when you run the AC. It's got an extended warranty so I was going to have the dealer look at it next week while I get an oil change, but from what I am reading about the smell, it may be the catalytic converters, is that a fairly common thing to just go out? Of course, the extended warranty specifically excludes cats too. I've tried the "spirited" 30-40 minute drive to get them hot and that seemed to help for a day or so but it keeps coming back. I let my parents use the car for 3 days and they noticed the smell as well. I don't smell it when walking around the car, or in the engine bay, it's really just inside the car from what I can tell, and only when the fan is on. The car is not throwing any codes either.

[M5Rick]

I used an a/c de-tox spray made by Magneti Marelli after changing the micro filters.
With the engine running and a/c on max cold and fan on full, empty the can through a slightly ajar front door, after emptying close door and let the engine tick over for about 15 minutes, then switch off opening all the windows to aerate the interior and it's done.

*Oh forgot just to add, it's important to have the vent on recirculate while the de-tox is working.

[passta]

So here is what ended up being the issue, which I had on my e39 several times and just didn't even think of it being a possibility here. The cowl drains clogged on both sides, so once it warmed up here, there was water and leaves and stuff in there which started decaying and that was the source of the smell, and that was on the outside part, nearest the fender and I just didn't notice it when I took the blower out as that all sits in a plastic tub of sorts. There was actually a tiny tree growing on the passenger side. I usually keep it garaged, but I live in a heavily wooded area so the opportunity for leaves and debris to collect in there exists. The dealer wanted $500 to clean it out, took me an hour with a shop vac and a hose, it drains fine now.

[texsn95]

Lol, pic of tiny tree?