I vented a gas water heater out through the wall instead of up through a flat roof. It has 12" vertical off the draft hood, a 90, 16" horizonal, 90, then 36" of vertical. Everything through the wall and outside is class b. It vents good now, just curious if it will vent when it's real cold? Oh, it 3" pipe.
Thanks

Mine does about the same amount of pipe,, should vent better in the cold,,, warm rises

Get a co2 sensor to be safe not worth taking a chance.

You want a CO detector for Carbon Monoxide.Co2 is Carbon Dioxide

What ever will save his life is what’s important. You are right carbon dioxide will not set off a carbon monoxide detector and a gas heater would give off carbon monoxide.

He is right, the colder it gets the better it will vent. If it is venting good then it will vent in the cold better.

Thanks guys. I'm a getting a detector.

Another safety consideration is to vent a proper distance from where the vented gas could re-enter the house, such as through an open window. It is specified in the international building code.

Everybody should have CO detectors anyway in their homes. It's the silent killer.

Our LP water heaters tank broke years back it was running continuously during the night trying to keep up. The CO alarm went off so I got up to see what was going on with it. I found water running on the floor and the tank struggling to keep up. I turned off the water and heater then aired out the place a bit a bit and went back to bed.

No telling how long that sleep would have been without that alarm working like it should have.