What are by-products of combustion?

Whenever something is burned, there are ‘leftovers” from the process.  It really doesn’t matter what is burned, wood, natural or LP gas, fuel oil, kerosene or coal.  These leftovers, or by-products include:  water vapor, carbon monoxide, nitrogen oxides, carbon dioxide, sulphur dioxide and other particulate matter.  Indoor air quality will be affected.  It can be a dangerous and even deadly scenario if these combustion by-products are not allowed to be expelled to the outside air.  Have the chimney system for your fireplace, stove, insert or furnace inspected annually by a certified technician.  The same goes for the vent system for your gas furnace, water heater and fireplace.