The international airports in Pennsylvania are Lehigh International Airport at Allentown, Erie International Airport at Erie, Harrisburg International Airport at Harrisburg, Philadelphia International Airport at Philadelphia,
Electric Plenum Heaters. A plenum heater is an electric resistance heating device that is installed in the plenum, which is the spot in the ductwork system where ducting and furnace join. Air is heated as it flows across electric elements and then is distributed through the existing ductwork.
Furnace Plenum. A plenum is a compartment, air space or chamber that is filled with air that is then distributed elsewhere. A furnace plenum then, is such an air chamber that gets filled directly (and quickly) by a large blower that is above, below or adjacent to it. Air ducts connected to a furnace or heater plenum carry this air to various registers around a house or building.