Why closethe air vent valve when white steam is coming out in boiler operation?

Closing the air vent valve when white steam is coming out of a boiler is essential to maintain proper pressure and ensure efficient operation. White steam indicates that water is vaporizing, and if air is allowed to escape, it can lead to pressure fluctuations and inefficient heating. By closing the valve, you help to create a sealed environment that promotes optimal steam production and prevents air from interfering with the heating process. Additionally, this practice helps to prevent potential safety hazards associated with uncontrolled steam release.