Odors / non-human source

There are mainly 2 other sources, a clogged in the vehicles ventilation systems or animal intrusion.

Ventilation caused odors if caught early can be handled with a system disinfectant that all manufacturers have in the parts department. It is best if a trained technician handles the procedure.(most of the time a evaporator hose needs to be unclogged or a related function needs to be performed.) If  the system has gone a while with a build up of the fungus due to sitting moisture; you may have a big problem. I've seen the entire vehicle stripped, rebuilt with new carpeting and seats. It still smelled, probably coming from the headliner or ventilation system.

Animal intrusion happens generally when the little critters are looking for nesting spot. They end up under the hood, sometimes chewing up wires and can usually be cleaned out. If they get too comfy and get further into the ventilation system, you may have quite a project.This is rare and usually happens in the fall or when a vehicle is not stored properly.