Air handlers and furnaces aren't often found in the same home in Gaithersburg. If you rely on a furnace, you probably shouldn’t need to consider an air handler.
Air handlers are often linked with heat pumps and deliver airflow across your home. Some models also offer backup heating and cooling parts to help the heat pump.
A furnace heats in a different manner by sending warm air into your vents, which circulate it throughout your home. Because furnaces rely on combustion chambers to make warmth, they don't use some of the pieces you'll spot in a normal air handler.