Western star 4900ex

Find a used car dealer or rental store that has an ozonator? Spelling.. sorry, put it inside, run it overnight, maybe long for a big bunk, then open it up and let it air out for a day. Will remove all smell. You can buy the machine cheap, but the cheap ones dont work as well is the commercial ones.
DONT drive it right away, let it air out. There are no chemicals, but whatever it does, you dont want to be in there for a while.

 

I'm sitting in a '21 right now, there's a small black screw on the bottom you need to remove. Every one I've driven has the screw in a slightly different location, so you may have to look around to find it. Last truck I drove it was on the left side near the front of the panel. This one doesn't have anything there. Seems like they put the screw wherever they want. We change those filters every six months, because we're always in dusty conditions. We take them panels off and leave them off, because they're a PITA.

There's actually two filters, (at least in the daycabs). One on top of the other. Kind of a pain to replace. They slide in, so you slide the first one in, and then have to hold it up with a screwdriver while sliding the second one in. We pull the fan motors out and clean the squirrel cage with the and the fan motor with air. Keeps the motor running quieter.
This is my third 4900 since '13, and those factory foam filters are junk. Alliance makes a paper filter that actually works well, I can get a part number later when I get back today.

 

Spray called ozium works pretty good at getting rid of smells too.

 

I cleaned mine up really nice and aired it out, but the smell of cigarettes would still pop up randomly. It wasn't until I renovated the interior that it totally went away. The insulation in the walls and ceiling smelled really strong when the cabinets came out.

 

If the dude did smoke 2 packs a day and smoked in the sleeper you ain't getting smell out for a while. It attaches to everything.

 

Vital Oxide is a good odor killing spray.