On Thu, 5 Jan 2006 07:35:29 -0800, "Steve B"
wrote:

If you suspect you or someone is affected, look at their nails. Cyanosis,
bluing of nailbeds and lips, is a sign.

That's usually a sign that they're already dead (or good as). CO is
hazardous enough that it has a good chance of killing long before
visible signs are evident. And for that matter they'll turn a deep pink
from CO, rather than blue.

For chronic low-level CO exposure, a slight headache might be all the
symptomatic indication you get. Then one day the wind is blowing the
other way down your gas heater flue and you wind up dead instead. Back
in the days of individual room gas heaters (coal gas) we really did lose
an awful lot of people to these accidents.