My furnace stinks. Any planning??? It doesn't come through the vents, but it smells up the crypt...

It doesn't come through the vents, but it smells up the crypt room where it is. It liberal of smells like burning or smoke, but I haven't be able to locate anything out of the usual.
How do I seize rid of moss on...
Answers:    1st heat cycle of the season usually smells close to burned dust in the duct.
How do I replace my sliding quad door?
tweaking the filter? check the ducts.. might be clogged with dust..