Abstract: The present invention relates to a polypeptide construct comprising at least two fragments of an allergen from the Amb a 1 family of allergens from Ambrosia atermisiifolia or variants of said at least two fragments, wherein each of the at least two fragments consist of 20 to 50 amino acid residues and wherein at least one fragment is derived from amino acid residues 1 to 50 of the mature allergen and at least one fragment is derived from amino acid residues 240 and ending at the C-terminal end of the mature allergen.

Abstract: The water heater has an upright water tank (1), an exhaust flue (3) extending through the water tank, a combustion chamber (2) arranged under the water tank, an atmospheric gas burner (5) in the combustion chamber and a complete pre-mixing gas/air supply system with outside gas and air intakes. The gas burner has a burner mat (7) with a pressure drop less than 5 to up to 45 Pa. The combustion chamber (2) is provided with an opening (2b), which is not sealed, but enclosed in a flame-blocking manner. The gas burner (5) is attached to a wall section (2a), which is mounted releasably on the: combustion chamber wall (W) over opening (2b) so that a gap of predetermined width is formed between the wall section and wall (W), which prevents backfire of flames into the surroundings but admits secondary air.