Abstract: A hot air blower, including: an air channel for blowing a main stream of air therethrough by an electric fan; a gas tank, for supplying burning gas; a gas burner, including: an air inlet, disposed within the air channel, for receiving a first portion of the main air stream; a burning gas inlet for receiving the burning gas; and an outlet, disposed within the air channel, thereby the gas burner produces a flame at the outlet within the air channel, for heating the main air stream; and a mechanism, for automatically fitting a size of the air inlet to an extent of the main air stream and consequently to an extent of the second portion thereof.