Doing an experiment here. I've got 20k miles on my 2022 m3p. The cabin filters and ac coils were stinky after about 6 months, and 12k miles. Not super impressed with the design and how the cabin filters get wet and nasty. So I am trying a solution to lengthen the cabin filter change interval.
I purchased some RMR-141 antifungal spray from slamazon. I removed the old air filters, sprayed the AC coils with some Kool it foaming cleaner. The tiny can lasted about 8 seconds and was empty. Barely enough to even clean the coils once. I ran the air for 15 min to let the AC coils dry out, then installed the new filters.
When the antifungal spray arrived a few days later I popped open the frunk, popped the first cover off over the HVAC fresh air intake. I turned the HVAC on, fan speed seven, ac off, recirculation off. The fresh air intake was pulling air nicely. I misted about 15 pumps of the antifungal spray into the intake. This should serve to deposit some of the spray into the cabin filters and the HVAC system. As the spray also serves as a fungistat/bacteriostat, it should help to prevent further fungal/bacterial growth in the cabin filter system and ac coils.
I took my wife out to dinner immediately after I sprayed the antifungal, and she nor I reported any chemical smells in the car. The spray actually doesn't have a smell, or if anything smells nice and clean.
I plan on refreshing the concentration of fungistat every month or so and see if any stickiness returns. I will update this post over time.
Level8drummer