Air handlers and furnaces aren't often found by each other. If you have a furnace you most likely don't need to consider an air handler. Air handlers are usually paired with heat pumps and help control airflow throughout your home. Some models also provide secondary heating and cooling pieces to help out the heat pump. A furnace works differently. Instead of an air handler, furnaces have blowers that send warm air into your vents, which circulate it across your home. Since furnaces have combustion chambers and make heat, they don't have some of the parts you'll find in a regular air handler.