Air handlers and furnaces aren't often installed in the same home in Knoxville. If you rely on a furnace, you probably won’t need to consider an air handler.
Air handlers are typically paired with heat pumps and deliver airflow around your residence. Some systems also have backup heating and cooling components to assist the heat pump.
A furnace runs differently by pushing warm air into your vents, which send it across your home. As furnaces depend on combustion chambers to make hot air, they don't use some of the components you'll see in a standard air handler.