TIA:

My circa 1949 rental house an 18 year old furnace with a flue chimney which
appears to be asbestos.
It's gray and hard and flat about 3" x 15" and fits inside a wall. At some
time it was moved, but not the whole thing, just the segment between the
attic and the basement, to accomodate a wall move on the ground (only)
floor. I guess they didn't want to re-do the roof so there's a "Z" in the
attic, about 2' of horizontal run of same material, with glue and sheet
metal at the two 90° joints. I think they also cut that horizontal piece out
of the entire run of chimney, as it hangs from joists in the crawl space,
and is flush with the roof deck on top.

1. Tentant smelled gas in the room where the chimney runs up the wall.
2. Gas Company measured some CO in the crawl space and made me shut off the
furnace, saying "there might be a crack in the heat exchange"
3. HVAC guy wants to sell me a new furnace, since "there might be a crack in
the heat exchange" (Didn't verify any crack)
4. Where the furnace vent tied into the asbestos was very loose, there was a
½" gap all around it, looked like a good place for CO to get out. I sealed
it real good at that point.
5. Gas Company came back and measured 0 PPM CO in crawl space. (NONE!) but
then they measured 10 PPM in the house, and turned off the furnace.
6. I went on the roof to see if the chimney was clogged, and at 2' I hit
something hard
7. I went in the attic and found the 2 right angles, and decided to go get
drunk. (Just kidding about that last part.)

(furnace is 18 years old but works)

Asbestos and age aside;

1. Is it conventional or kosher to have a horizontal run in the flue vent
for the furnace/water heater?
2. Where the chimney is flush with the roof, it's not sealed, should the
chimney extend above the roof line?
3. Is there any kosher way to run the flue inside a wall nowadays?
4. I know I can vent a 90% or better furnace out the side with PVC, can I
vent the water heater out the side, legally?
5. What am I forgetting?