Thanks Brian,

Thanks to everyone who responded. Concencus seems to be about 40 hours
or in that vicinity.

I'll check with my insurance agent on the gas bottle inside. I can
always drill a hole through the wall and run a hose with bottle outside
on the patio.

As to the few comments on non-vented they are as safe as any other form
of heating. Modern ones have an ODS (Oxygen Depletion Sensor) that
shuts gas off before CO gets too high. Of course I would still have a
Nighthawk CO sensor which actually has a readout of the levels rather
than just a warning beeper if too high.

Thanks again guys, I will wive it a shot.

Dave