Heating when the power is off.

[Mortblanc]

As said, ventilation is the sensible, universal answer.

My Buddy Heaters all have O2 sensors that shut them off if they overload. That technology has been standard for 50 years now.

Your house is probably not as "air tight" as you suppose. Just a slightly cracked window is enough. Many is the time I went through a house the family just moved into and had to seal up the light switches and plug panels with plastic because a virtual wind was whistling in!

Today I do not need heat but I am sitting and watching the drapes over the doors and windows move with the air currents imposed by a steady 50mph south wind. My doors are covered by plastic, canvas and wool blankets and I can assure you there is plenty of oxygen available if I decided to light a heater.

Pete, do you have a filter in that gas hose? Rubber leaches into the line and stops up the burner jets if not.