What type of gases contribute to a stronger draft in a venting system?

Hot exhaust gases contribute to a stronger draft in a venting system due to their lower density compared to colder gases. When gases are heated, they expand and rise, creating a pressure difference that helps to draw more air into the system for combustion. This effect is known as the stack effect or natural draft, where the warmer, lighter gases rise through the vent and are replaced by cooler air from outside, further enhancing the overall efficiency of the venting process.

In contrast, cold exhaust gases are denser and do not rise as effectively, leading to weaker drafts. Polluted gases and non-combustion gases do not significantly contribute to the effectiveness of a venting system as they lack the heat necessary to create the necessary pressure differential for a strong draft. Thus, hot exhaust gases are critical for ensuring an efficient and effective venting system.