Which type of furnaces and boilers require combustion air for operation?

Fuel-fired furnaces and boilers require combustion air for operation because they rely on burning fuel to generate heat. The combustion process requires oxygen, which is obtained from the surrounding air. Proper ventilation must be maintained to ensure that an adequate supply of combustion air is available, supporting clean and efficient burning of the fuel. If the air supply is insufficient, it can lead to incomplete combustion, producing harmful gases and reducing the system's efficiency.

In contrast, electric furnaces use electrical energy to produce heat, eliminating the need for combustion air. Heat pumps operate by transferring heat rather than generating it through combustion, and solar heating systems harness energy from the sun, meaning they also do not require combustion air for their operation.