there is a very strong dust odor

Make sure the drain is open for the AC. It should be a black rubber hose coming out at the firewall. As far as a filter, none exist to the best of my knowledge.

Also, is the smell that of coolant? The heater core could have a pinhole which can cause a bad smell too.

Thanks for the reply however I am certain that the drain works fine and the heater core is good. I am a diesel mechanic so I do have some knowledge in the area. The smell is definately a dusty smell, not coolant or stagnated water. On a semi there is a replaceable filter near the evaporator. I was hoping for something similar. There are also businesses here that can freshen it for a pricey fee but they will not tell me how. Again, Thanks a bunch and any more help is appreciated.

Hi:
I just double checked, and I find no listing for a cabin air filter. Based on that, I would say it doesn't exist. I wish I had better news.