In a forced draft system, what design feature is crucial for maintaining safety during operation?

In a forced draft system, gas tightness is a critical design feature for maintaining safety during operation. This attribute ensures that gas leaks, which can pose serious safety hazards such as combustion risks and exposure to harmful gases, are effectively minimized. Gas tightness involves the integrity of the system's seals, joints, and components, preventing any unintentional release of gases into the environment.

By maintaining a gas-tight system, the risk of fire and explosion is significantly reduced, as the combustion process relies on controlled conditions where gas and air are properly mixed and delivered to the burner. If any part of the system is not gas tight, it could result in dangerous situations, including the potential for carbon monoxide buildup or unregulated combustion.

In contrast, while features like inspection hatches, pressure sensors, and heat shielding contribute to the overall safety and efficiency of mechanical systems, they do not address the critical need for controlling gas emissions as directly as gas tightness does. Therefore, ensuring that the forced draft system is properly sealed and gas tight is essential for safe operation.