Converting from single furnace to four - chimney question

[Craig Shrimpton]

All,

I'm looking at a four unit building that has a single furnace with four zones. The chimney is presently power vented through the wall as there is no chimney.

If I add three more furnaces and power vent them like the existing one, I would gas out the first floor apartment.

My question is what kind of venting solution is available short of building a four flue masonry chimney?

There seems to be reference to a setup that will allow multiple furnaces to vent into some kind of specially engineered pre-fab chimney, but it's a bit confusing trying to figure out what's legal, safe and available.

Anyone solved a problem like this? If so, how did you do it?

Thanks,

Craig