What is the primary purpose of a boiler's combustion air fan?

The primary purpose of a boiler's combustion air fan is to supply air for combustion. In any combustion process, sufficient air is necessary to ensure that fuel burns efficiently and effectively. The combustion air fan draws in ambient air and directs it into the combustion chamber where it mixes with the fuel. This mixture is essential for achieving proper combustion conditions, which contributes to optimal boiler performance, efficiency, and emissions control.

Without adequate air supply from the fan, the combustion process can become incomplete or inefficient, leading to potential safety risks, increased emissions, and reduced energy output. This highlights the critical role that the combustion air fan plays in supporting the overall operation of the boiler by ensuring that the fuel is burned efficiently. The other options relate to different aspects of boiler operation that are not directly related to the function of the combustion air fan.