In article ,
Mike D writes:

Does anyone know what are the effects of breathing small amounts of
natural gas, over a long period? I did a search and couldn't find any
info.

I think it's harmless, unless there's enough to significantly
reduce the oxygen concentration, but there would be no question
of an incredibly strong smell.

Several people (including myself) have noticed a slight smell of gas
in my house, occasionally, in certain odd locations (like half way up
the stairs) or just as you enter one upstairs room. I had Transco out
but they couldn't detect anything. Still, I'm not convinced.

Some boilers often emit some unburned gas from their flue when
they light. Is it possible there's some boiler flue gas getting
back in the house?

I've been suffering from extreme tiredness for several months, and
wonder if it could be caused by breathing small amount of gas while at
home.

That could also be consistent with boiler flue gas getting back
in the house.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]