Recycling air mixer for heater unit

For use with a portable warmed air heater including an engine, a heat generator, a heat exchanger to transfer from said exchanger to said air and means for moving said air;

• a housing enclosing said engine, heat generator and heat exchanger, said housing having an intake end and an exit end, a duct formed in said housing leading from said exit end to said intake end to allow air to be recirculated from said exit end to said intake end, a chamber formed in said intake end of said housing, intake means formed in said chamber for allowing ambient air to enter said chamber, control means in said chamber for controlling the proportions between the shares of ambient inlet air and of recirculated inlet air and a sensor device at said exit end for sensing temperature of air leaving said housing, said sensor device being operably connected to said control means to adjust said control means for adjusting said shares to provide a satisfactory exit air temperature.