Thom,
CO detectors are inexpensive; I keep one in my cabin (I have a propane
burner and lantern).
I guess the CO2 could be problematic if the levels rose too high, but at
least it's non-toxic.
"Alcohol heaters consume oxygen. As O2 levels in an enclosed space fall,
fuel is incompletely burned and carbon monoxide is produced. A clue this
is happening is that a normal blue flame becomes yellow and smoky."
http://www.carbonmonoxidekills.com/boats.htm
Scout


"Thom Stewart" wrote
Now, I've been doing this for meany years, without vents. I know the
alcohol flame does delete the oxygen level. It's worried me but not
enough to vent in cold winter air. I could use some useful comments?