Sorry, this isn't really forced-air
Here are some shots of the boiler in the building where I work. It hasn't been used in many, many years, but it's still there. It has to be -- there's really no way to get it out of the building. You'd have to remove the building from around it.
Our shop is located in what was, in days past, the showroom and offices for a car dealership. We don't know exactly when the original section of the building was built, or what it was built for. We're pretty sure it was built in the early 1900s.
It's been built onto and remodeled several times. The section where the boiler is located was probably added in the years immediately following World War II, when the automotive industry (like so many industries) was booming.
It's our guess that the boiler was originally coal-burning, but that it was converted to natural gas at some point. You can see in the pictures below that it has the sort of doors with adjustable vents that you'd expect on a solid-fuel furnace.
As part of the natural gas conversion (presumably), a combustion-air blower was added to the front of the firebox (shown in the bottom picture). Unfortunately, it sticks so far out of the front of the thing that the boiler-room door no longer opens all the way. That's why the pictures only show half(!) of what's there. You can get an idea of scale from the normal-sized door in the foreground.
This thing is really huge, and it's kind of scary -- it's the sort of thing you'd expect to show up in a Stephen King movie. People in the movie who ventured into the boiler room would not meet with a happy fate.
-kevin
