Central heating and cooling equipment is used to maintain, repair, and replace components of HVAC systems that use ductwork to distribute heat and air conditioning from a single furnace or cooling unit to multiple rooms. This central equipment is typically installed and serviced by HVAC technicians. Furnaces produce heat for central heating by burning natural gas or another fuel. Air handlers, condensing units, and evaporator coils are components of central air conditioning units, split system air conditioners, and heat pumps.