An adjustable device for varying the size of the air inlet or inlets regulating primary or secondary air would be

An adjustable device for varying the size of the air inlet or inlets regulating primary or secondary air would be

• A. Draft hood
• B. Air shutter
• C. Regulator vent
• D. Orifice

Answer: (B)

Controlling the amount of air entering the burner to tune the flame is done with an adjustable air shutter. This device changes the size of the air inlet(s) around the burner, allowing you to regulate primary air that mixes with gas at the burner and secondary air that is drawn in around the burner assembly. By opening or closing the shutter, you can adjust flame characteristics, efficiency, and combustion stability under different operating conditions. The other components serve different roles. A draft hood is part of the venting system, helping prevent backdrafts and assisting exhaust flow; it isn’t used to adjust the air for combustion. A regulator vent is related to venting or safety relief for the gas pressure regulator, not to air control at the burner. An orifice meters gas flow through a fixed hole and does not adjust air intake.

Controlling the amount of air entering the burner to tune the flame is done with an adjustable air shutter. This device changes the size of the air inlet(s) around the burner, allowing you to regulate primary air that mixes with gas at the burner and secondary air that is drawn in around the burner assembly. By opening or closing the shutter, you can adjust flame characteristics, efficiency, and combustion stability under different operating conditions.

The other components serve different roles. A draft hood is part of the venting system, helping prevent backdrafts and assisting exhaust flow; it isn’t used to adjust the air for combustion. A regulator vent is related to venting or safety relief for the gas pressure regulator, not to air control at the burner. An orifice meters gas flow through a fixed hole and does not adjust air intake.