I ask out of ignorance

"Char Jackson" wrote in message
...
Back in the 90's, a friend of mine was feeling sick in the evenings when
she was home and fine during the day when she was at work. Likewise for
her son - sick in the evenings and fine at school. After a few days of
that, her furnace failed and she brought in a repairman. He discovered
that the flue was plugged by a squirrel nest and the furnace exhaust had
been venting into the basement. She and her son were lucky they were
able to wake up each morning while that was going on. Neither of them
smelled anything unusual. If she'd had a CO detector, I'm sure it would
have gone nuts.

My parents have a holiday cottage which has a coal- and wood-burning stove.
Some friends were staying there and started to feel dizzy and sick one
night. Luckily one of them recognised the symptoms - and the flushed red
face of one of the other friends - and got them outside into the fresh air.
The fire brigade came and detected high levels of CO. It gave my dad a real
fright to think that his stove could have been responsibility for the deaths
of three friends.

I'm not sure whether a fault was found with the stove or the flue. The stove
has since been changed, though I think because other parts had started to
fail, not primarily because of the CO incident.

We now have CO detectors in various rooms - not only the room where the
stove is, but also adjacent rooms and the one above it, because I think CO
is roughly the same density as air so it will rise in the same way as hot
air rises, if any *does* escape.

CO levels vary between zero (below detectable level) and about 20 ppm. The
literature with one sensor says that 40 ppm is the safe maximum for
continuous exposure. The sensor only seems to register non-zero levels for a
while after the ash pan is removed in the morning to empty it - I imagine
the ash gives off a certain amount which goes into the room as the ash pan
is being taken outside instead of going up the chimney.

The bigger problem with the ash is acrid, sulphurous (*) fumes which tend to
be noticeable if the ash bucket has to be kept inside (in a room that is not
normally used) to avoid the bucket getting rained on; when there's no rain
the bucket lives outside until the ash has cooled enough to put into a
plastic coal bag to go in the bin.

(*) I wonder if it's sulphuric acid amongst other things. It's an SO2 rather
H2S smell - acrid rather than rotten eggs. I presume coal briquettes
("Phurnacite") still contain a fair amount of sulphur, even though a lot of
the tar of normal coal has been removed by part roasting.