1) Many ranges *do* have a flue of sorts-- the range hood which ideally
vents outside
2) The BTU output of a range pales in comparison to a furnace or WH
3) The typical range is only used a fraction of the time of the typical
furnace or WH
-Tim
When you use a gas stove without a range hood venting to the outside
you are actually using a tiny ventless heater. Years ago people didn't
worry about air quality as much and homes were less tight. Many people
get a headache when the stove is on and the unburned gases are the
reason. It is suggested that a window be open at least a little when
using a gas stove.