Which adjustment might be necessary if a burner is smoking excessively?

When a burner is smoking excessively, it often indicates that there is an imbalance between the fuel and air mixture being delivered for combustion. A common cause of this issue is that there is not enough air mixing with the fuel, leading to incomplete combustion and the production of smoke.

Adjusting the air shutter is a direct method of increasing the air supply to the burner. By properly tuning the air shutter, you can optimize the air-to-fuel ratio, ensuring that there is enough oxygen available for the fuel to combust completely. This adjustment can help eliminate the excess smoke and improve overall burner efficiency.

The other options do not address the core issue as effectively. While increasing fuel pressure may seem beneficial, it could exacerbate the problem by delivering even more fuel without sufficient air to combust it. Decreasing combustion air would make the situation worse by further limiting the oxygen available, while cleaning the nozzle, although important for maintenance, may not directly solve the issue of smoke if the air supply is still insufficient.