conveyor 12 hot air is forced from the heater blower assembly 40 through the outlet vents and is directed into the wrapped load l because the tunnel side wall assemblies 14 are adjusted to contact or nearly contact the inner perforated wall 34 and the edges of the sleeve s the hot air is essentially all directed into the sleeve s rather than into the space around or outside of the load l within the tunnel 10 moreover because air is drawn into the plenum 36 through the perforated plates 34 there is a higher pressure region created within the sleeve s which further facilitates drawing the air from sleeve s around the load l essentially a high pressure region is created at the blower 40 discharge with a low pressure region created within the plenum 36 in addition because the sleeve s edge is positioned to contact or nearly contact the perforated wall 34 the hot air blown into the sleeved load l see e g fig3 is drawn out at the top and bottom of the sleeve thus facilitating the flow of heated air and rapid heat exchange to the shrink wrap material it will be appreciated by those skilled in the art that the relative directional terms such as upper lower rearward forward and the like are for explanatory purposes only and are not intended to.