My experience (sample of one) is that they don't. They're supposed to, but VOCs are definitely higher all winter running heat than all summer running air conditioning. Natural gas combustion is at best _mostly_ exhausted.
> My experience (sample of one) is that they don't.
There is something very very wrong with your equipment (or you're measuring something else not having anything to do with the heating equipment - more likely). A high efficiency furnace has a sealed combustion chamber, the entire thing runs in a circuit vented to the outside - combustion air comes from the outside and it is vented to the outside. If it is not airtight sealed from the indoors, it is broken. Even a mid-efficiency furnace with a non-sealed system will vent 100% of the flue gas outside.
> Natural gas combustion is at best _mostly_ exhausted.
Bullshit for any modern equipment (ie installed in the last 50 years).
It could also be that outdoor AQ is worse around you in the winter because everyone is running their boilers, and then that outdoor air ends up inside. I can't test it because I have a heat pump, but I would be curious to know what happens to your VOCs if you turn off your boiler at a time when your neighbors are still running theirs.
There is something very very wrong with your equipment (or you're measuring something else not having anything to do with the heating equipment - more likely). A high efficiency furnace has a sealed combustion chamber, the entire thing runs in a circuit vented to the outside - combustion air comes from the outside and it is vented to the outside. If it is not airtight sealed from the indoors, it is broken. Even a mid-efficiency furnace with a non-sealed system will vent 100% of the flue gas outside.
> Natural gas combustion is at best _mostly_ exhausted.
Bullshit for any modern equipment (ie installed in the last 50 years).