Which characteristic does a sealed combustion appliance possess?

A sealed combustion appliance is designed to draw combustion air exclusively from outside the building rather than from the indoor environment. This characteristic is crucial for ensuring safety and efficiency, especially in tightly sealed homes where indoor air quality could be compromised. Since the appliance draws in air from the outside, it prevents the potential hazards associated with depleting the indoor oxygen levels and reduces the risk of back drafting, where exhaust gases can be pulled back into the living space.

By utilizing outside air, sealed combustion appliances can operate without relying on the indoor conditions, making them ideal for environments that are well insulated or have limited ventilation. This also allows for better control of combustion efficiency, as the appliance can utilize a consistent and potentially more regulated air source for burning fuel.

This design feature highlights the focus on safety and performance, which distinguishes sealed combustion appliances from traditional models that may introduce air from surrounding indoor spaces.