Products of combustion plus excess air plus dilution air (on natural-draft appliances) that pass through the vent
The gases emitted to atmosphere from a production or combustion process through the flue or "smoke stack"
The exhaust gases from a combustion facility in the stack that discharges them to the atmosphere These gases often contain sulfur, which can be removed by a desulfurization scrubber, and particulates, which can be removed using specialized collectors like electrostatic precipitators, mechanical collectors (cyclones), fabric filters (baghouses), and wet scrubbers
The air coming out of a chimney after combustion in the burner it is venting It can include nitrogen oxides, carbon oxides, water vapor, sulfur oxides, particles and many chemical pollutants