WHOA Hud... hang on there bud, don't go venting combustible hobby fumes
into your heating & AC ventilation system, I'm assuming that you're
talking about enamels here.
HVAC systems don't really exhaust to the outside, they re-circulate the
same air with "some" new outside air added. So your fumes will be
traveling throughout the house, if it makes it safely past the furnace.
If you don't have a window that you can use to vent through, and I can
understand not wanting to bore a hole through your foundation, what
about going through the header above the foundation? You can then use a
dryer vent from outside of the house.