Air handlers and furnaces aren't often installed side by side in Saint Charles. If you rely on a furnace, you probably won’t need to consider an air handler.
Air handlers are typically used with heat pumps and deliver airflow throughout your home. Some units also have backup heating and cooling pieces to support the heat pump.
A furnace heats in a different manner by blowing heated air into your vents, which circulate it throughout your home. As furnaces have combustion chambers to create warmth, they don't have some of the components you'll find in a regular air handler.