What happens when combustion gases become too cold?

When combustion gases become too cold, the water vapor present in the flue gases will condense back into water. This phenomenon occurs because combustion produces water vapor as a byproduct, and when the temperature of these gases drops to their dew point, the vapor changes state from gas to liquid. This condensation can lead to water accumulation in the chimney or venting system, which is problematic as it can cause corrosion of the materials and potentially create blockages.

The other options do not accurately reflect the consequences of cold combustion gases. For instance, a colder temperature does not lead to an increase in combustion rate; rather, it suggests less efficiency in the combustion process. Similarly, while cooler gases might lead to some particulate matter not being fully combusted, this does not necessarily result in an increase in smoke production. Lastly, cold gases do not rise more easily through the chimney; in fact, they tend to lose buoyancy, which can hinder their ability to move upwards through the venting system efficiently.