What action during operation will prevent the boiler from emitting heavy smoke from the exhaust stack?

Opening the air band during boiler operation significantly enhances the combustion process by allowing more air to mix with the fuel. This increased airflow ensures that the fuel burns more completely, which is crucial for minimizing smoke emissions. When there is adequate air supply, the combustion is more efficient, which leads to fewer unburned hydrocarbons and particulate matter being released into the exhaust.

Heavy smoke from the exhaust stack typically results from inefficient combustion, often caused by a lack of sufficient oxygen. By adjusting the air band to allow more air into the combustion chamber, you promote complete combustion, thereby reducing the volume of smoke produced. This is especially important in maintaining environmental compliance and achieving desired operational efficiency.

On the contrary, other options would either restrict the airflow or alter the fuel pressure without optimizing air-fuel mixing. Closing the air band can exacerbate smoke emissions due to insufficient oxygen for combusting fuel, while changes in fuel pressure alone do not address the combustion efficiency related to oxygen availability.