Abstract: The invention relates to a method and air curtain for restricting heat transmission through a wall opening (120). Using the method according to the invention, an air curtain restricting heat transmission will be formed in front of the door opening. In the method on the first edge of the opening a blowing air flow going through a blow nozzle (12) is formed using a blower (20), and on the other edge of the opening a sucking air flow going through the suction opening (16) is formed. Advantageously the blowing air flow is formed at the lower edge of the opening and the sucking air flow at the upper edge of the opening. In this way, an air jet (40) will form in front of the door opening going from the blowing nozzle to the suction opening, and induced flows (42, 44) of air will form on both sides of the air jet, together forming an air curtain. The flowing of air through the door opening between the air jet and the vertical edges of the opening is reduced by side wallings (32).