Abstract: A direct vent gas baseboard heater has field installable concentric air intake tube and exhaust pipe. The intake pipe and exhaust tube can be cut separately from the remainder of the heater, improving the efficiency of installation. They can also be transported aligned with the remainder of the heater, reducing packaging size. The manufacturer can provide a single size of tube and pipe for a variety of installation situations. The tube connects to a base cabinet through a key hole configuration of tabs and cuts, and is twisted until the tabs meet stops in the base cabinet. An extrusion in an air box in the base cabinet is brought against a gasket on a flange on the tube, fixing the tube and sealing it with the air box. The exhaust tube has a threaded end and is threaded into an exhaust outlet in the air box, sealing is to a heat exchanger. A vent seal kit creates a seal assembly having a resiliently deformable ring seal extending into a wall sleeve with straps.