https://www.serviceexperts.com/faq/what-is-the-difference-between-an-air-handler-and-furnace

Air handlers and furnaces aren't typically installed in the same home in North America. If you have a furnace, you most likely won’t need to think about an air handler. Air handlers are frequently paired with heat pumps and manage airflow across your residence. Some systems also provide extra heating and cooling pieces to support the heat pump. A furnace heats in a different manner by pushing heated air into your vents, which send it across your residence. Since furnaces depend on combustion chambers to produce heated air, they don't have some of the parts you'll see in a standard air handler.

What is the Difference Between an Air Handler and Furnace?

Air handlers and furnaces aren't typically installed together in Calgary. If you use a furnace, you likely won’t need to consider an air handler.

Air handlers are often used with heat pumps and manage airflow throughout your home. Some models also offer secondary heating and cooling components to support the heat pump.

A furnace works differently by blowing warm air into your vents, which send it around your home. Since furnaces depend on combustion chambers to make heat, they don't use some of the components you'll find in a standard air handler.