Ventilation system

I have seen dead mice leaves debris etc cause bad smells but most of the time its caused by people always using there recirculation with there a/c and not turning there a/c and recirculation off and there blower fan speed on high to dry all the water off the evaporator core for the last 2 mins of there trip.What that does it that left over water just sitting there grows bacterial spores that cause the bad smell and arent so good for you.I would have it checked out to make sure there isn't leaves debris etc and have the a/c cleaned i know a product called dwd2 cleans the a/c evaporator core real well i used to use it and it works great.Its for a professional to use though.