If CO levels increase from 50 ppm to 600 ppm and the overfire fan is indicated to be at 0% airflow, what should be checked?

When CO levels rise significantly, indicating a potential combustion issue, it is critical to assess the efficiency of the system, particularly airflow components. If the overfire fan shows 0% airflow, it suggests that there is no air being provided for combustion, which can lead to incomplete combustion and increased CO production.

Checking the fan belt on the overfire fan is essential because a malfunctioning or broken belt would prevent the fan from operating, resulting in no airflow. Without proper air intake, the combustion process can become inefficient, leading to higher carbon monoxide levels. Thus, ensuring the mechanical components, like the fan belt, are functioning correctly can help restore proper airflow and improve combustion efficiency, reducing CO emissions.

Addressing the fan belt is a crucial first step before considering other aspects related to combustion, such as fuel pressure or combustion temperature. While other parameters are important for overall system health, in this particular scenario, the immediate concern is airflow, as indicated by the overfire fan's status.