Ducts between garage and house - Fire Hazard?

I'm putting my new HVAC system in the garage: a Trinity boiler, B-W indirect water heater, and Goodman variable-speed counterflow air handler with hydronic coil and evap. They'll be located on the wall between the house and garage on a platform raised to the level of the house. The supply duct will go down, underneath, and through the foundation wall into the crawlspace. The return will start in the house attic, into the garage attic and down into the A/H.

I realize now that the garage & house are supposed to be separated by fire-rated walls & doors. I plan to enclose the equipment to exclude workshop dust, so I can use 5/8" drywall on that. But what about the ducts above and below? Maybe I can also enclose the sections that are in or above the garage. Is this a big concern?

There's no building permit involved, but I like to build to code anyway.

Jim,
they make a smoke and fire damper that you can install in line with the duct work. We have had to install them on past jobs. I would head to your local supply house for info

Lou

Several issues here.
(1) Who told you no permits?
(2) At one point, furnaces were routinely put in garages. This was before there were firewall codes. When I see it done today, they seem to box the ductwork in a soffit, built to firewall code.
(3) If you enclose the furnace in a room, now you have combustion air issues to deal with. You need to consult the National Fuel Gas Code about this.