A reverse combustion type combustion apparatus (1) includes a combustion section (2) that combusts fuel in a downward direction, heat exchangers (4, 5) disposed under the combustion section (2), and an exhaust box (6) disposed under the heat exchangers (4, 5). The exhaust box (6) is a molded product made from a synthetic resin material; the exhaust box (6) includes an opening portion (30) for introduction of combustion exhaust gases generated by an upper portion, a fixing portion (33) for fixing the heat exchanger (5), and an inclined bottom portion (35) that collects condensed water generated by the heat exchanger (5); and, at the lower end portion of the exhaust box (6), at least three legs (40) are integrally formed and make the exhaust box (6) stand up by itself.

A highly efficient indoor heating system and device is described. The device is equipped with an internal chimney, as well as vents that are configured to maximize the draft applied to the flame housed within a stove combustion area. The heater is configured to reach temperatures exceeding 300 degrees Fahrenheit in approximately ten minutes. A gravity fed fuel tube, potentially in communication with a wood pellet hopper, is configured to deliver fuel to the stove of the heater. Heat is distributed throughout the structure of the device, and a convection chamber within the device ensures that heat generated is not quickly lost via exhaust.