Abstract: A heat exchanger for receiving heat from hot exhaust gases flowing through the flue of a furnace or boiler. The exhaust gases are directed through a heat box which contains a plurality of tubes. A blower blows room air through the tubes whenever hot gases are flowing through the flue and the heat in these gases flows about the tubes to warm the air flowing through the tubes and the warm air is directed to a room to be heated. The exterior of the tubes are exposed to the exhaust gases and these become dirty and must be cleaned. To facilitate this operation the present invention provides for constructing the tubes into an assembly which is removable as a unit from the heat box and is secured to the box by snap moldings which snap over the open edges of the heat box and the tube assembly to not only secure the tube assembly to the heat box but to seal the heat box to prevent the escape of any gases.