A thermoforming apparatus for forming a blank into a composite article. The thermoforming apparatus includes a forming tool. A forming member forms the blank over the forming tool. A first chamber is arranged for containing the blank. A second chamber is separated from the first chamber by the forming member. A first air circulator is configured to circulate air in the first chamber for achieving a heat distribution to the blank. The first air circulator includes a controllable valve member. The apparatus also includes a second air circulator. A method for forming a blank during circulation of air in a first chamber.