Air handlers and furnaces aren't often found in the same system. If you have a furnace you likely don't need to consider an air handler. Air handlers tend to be paired with heat pumps and help control airflow throughout your home. Some models also include secondary heating and cooling components to aid the heat pump. A furnace functions differently. Instead of an air handler, furnaces have blowers that deliver warm air into your vents, which circulate it throughout your home. Since furnaces have combustion chambers and make heat, they don't have some of the parts you'll find in a normal air handler.