Abstract: A heat exchanger operatively arranged, like a sliding drawer in a dresser, to be urged through opposite direction sliding movement to facilitate its positioning at and removal in relation to a heat exchange station within a flue, or the like, of a heating system, with the result that it is readily easy to service and maintain the unit clear of soot and other clogging materials. Since, as noted, the problems associated with clogging are significantly obviated, the heat exchanger, among other advantages, can embody in its construction closely spaced heat exchange fins to greatly enhance the amount of heat extracted from the exiting flue gases.