Which of the following is a characteristic of a fuel-fired heating system?

A fuel-fired heating system relies on the combustion of fuel, such as natural gas, propane, or oil, to generate heat. For this combustion process to occur efficiently and safely, the system requires a specific amount of air, known as combustion air. This air is essential for the chemical reaction that takes place during combustion, allowing the fuel to burn properly. If there is not enough combustion air, the system can produce carbon monoxide and other harmful byproducts, posing safety risks.

While electric heating systems may operate without requiring combustion air and do not utilize fuel, this does not apply to fuel-fired heating systems. Moreover, external air sources may be used for combustion in some systems, but many require that a dedicated means of air supply is provided. Adequate ventilation is also necessary in fuel-fired systems to ensure proper air exchange and prevent the buildup of harmful gases. Thus, the requirement for combustion air is a defining characteristic of fuel-fired heating systems.