Ray wrote:
I live in an old six-unit apartment building which is heated by
oil-burning furnace.

For most of the time on cold days, we can see a fair amount of steam
coming out of the chimney.

Obviously some heat is being lost. The question is whether this is
normal. I don't recall seeing this steam coming out of other older
buldings in our area.

Is it steam or is it a cloud - smoke. Steam is 212º or hotter. :-)

I suspect it is just condensing water vapor. You burn hydrocarbons and
you get H²O and CO and CO² plus heat. When this mix hits the cold air it
condenses the H²O.

--
Joseph Meehan

26 + 6 = 1 It's Irish Math