jan wrote:

We live in a one story home that has a central 4-ton hvac unit.
Recently I've noticed that after the A/C kicks on, I get a heavy dose
of a smoke smell. Badly enough to where my eyes(burning) and
mouth/throat are affected.
SNIP

Could well be a failing motor in the air handler in the attic.
It may not be getting hot enough (yet!) to produce visible smoke in
the airstream out of the registers.

If you're not experienced opening the air handler and working
on motors, etc., get a pro out real soon.

Jim