What is a common characteristic of high-efficiency forced air systems?

High-efficiency forced air systems are designed with sealed combustion systems as a key characteristic. This feature allows these systems to draw in air from outside for combustion rather than using the air from inside the home. This improves safety by preventing combustion byproducts from entering the living space and enhances efficiency since the system can operate at optimal efficiency without affecting indoor air quality.

Sealed combustion systems also lead to reduced energy consumption because they minimize heat loss associated with conventional systems that rely on indoor air. By eliminating the risk of backdrafts and ensuring a more controlled combustion process, these systems are able to maintain higher efficiency levels compared to traditional forced air systems.

This focus on efficient combustion is part of what contributes to the overall energy savings and enhanced performance of high-efficiency forced air systems, making option B the correct choice.