A heat exchange cell for a heating condensing boiler, comprising: - a heat exchanger comprising at least one tubular pipe adapted to be traveled by a fluid to be heated, helically wound about a helix axis (L-L) according to a plurality of helix turns (12, 13, 14), and defining a free central space configured to form a combustion chamber, said heat exchanger ending with a first end helix turn and an opposite last end helix turn evaluated along said helix axis (L-L); - a container casing containing said heat exchanger mounted therein, comprising a side casing wall arranged radially outside and about said heat exchanger forming a fume collection chamber radially interposed between said exchanger and said side casing wall adapted to receive combustion fumes generated in the combustion chamber once said fumes have transferred an amount of heat to said fluid to be heated in said at least one tubular pipe, said container casing further defining a front casing end comprising a casing opening surrounded by an annular casing edge having the center on said helix axis (L-L), wherein said first end helix turn of said plurality of helix turns (12, 13, 14) faces said casing opening; - an annular closing flange arranged coaxial to said helix axis (L-L) defining a radially outer annular flange edge portion and a radially inner annular flange edge portion with respect to said helix axis (L-L), the radially outer annular flange edge portion being continuously and sealingly coupled to said annular casing edge, and the radially inner annular flange edge portion defining a central flange opening for allowing access inside the combustion chamber; - and wherein said closing flange comprises an annular contact portion coaxial to said helix axis (L-L), said annular contact portion being sealingly arranged in direct contact with at least one corresponding annular portion of the outer surface (13") of said first end helix turn; - and wherein said closing flange comprises an annular sealing portion coaxial to said helix axis (L-L); - a removable closing door configured to removably close said central flange opening when said closing door is tightened to said closing flange in a closed position, said closing door defining an annular door edge portion configured to be coupled to said annular sealing portion of said flange; - wherein said annular sealing portion of said closing flange is arranged not in contact with, and detached from, the outer surface of said first end helix turn and delimits, in part, said fume collection chamber; and - wherein said annular sealing portion of said closing flange is arranged, at least in part, radially outside said annular contact portion, according to a radial direction orthogonal to the helix axis (L-L), characterized in that: - said closing flange is made of a sheet metal and is entirely formed by molding in a single piece. - a heat exchanger comprising at least one tubular pipe adapted to be traveled by a fluid to be heated, helically wound about a helix axis (L-L) according to a plurality of helix turns (12, 13, 14), and defining a free central space configured to form a combustion chamber, said heat exchanger ending with a first end helix turn and an opposite last end helix turn evaluated along said helix axis (L-L); - a container casing containing said heat exchanger mounted therein, comprising a side casing wall arranged radially outside and about said heat exchanger forming a fume collection chamber radially interposed between said exchanger and said side casing wall adapted to receive combustion fumes generated in the combustion chamber once said fumes have transferred an amount of heat to said fluid to be heated in said at least one tubular pipe, said container casing further defining a front casing end comprising a casing opening surrounded by an annular casing edge having the center on said helix axis (L-L), wherein said first end helix turn of said plurality of helix turns (12, 13, 14) faces said casing opening; - an annular closing flange arranged coaxial to said helix axis (L-L) defining a radially outer annular flange edge portion and a radially inner annular flange edge portion with respect to said helix axis (L-L), the radially outer annular flange edge portion being continuously and sealingly coupled to said annular casing edge, and the radially inner annular flange edge portion defining a central flange opening for allowing access inside the combustion chamber; - and wherein said closing flange comprises an annular contact portion coaxial to said helix axis (L-L), said annular contact portion being sealingly arranged in direct contact with at least one corresponding annular portion of the outer surface (13") of said first end helix turn; - and wherein said closing flange comprises an annular sealing portion coaxial to said helix axis (L-L); - a removable closing door configured to removably close said central flange opening when said closing door is tightened to said closing flange in a closed position, said closing door defining an annular door edge portion configured to be coupled to said annular sealing portion of said flange; - wherein said annular sealing portion of said closing flange is arranged not in contact with, and detached from, the outer surface of said first end helix turn and delimits, in part, said fume collection chamber; and - wherein said annular sealing portion of said closing flange is arranged, at least in part, radially outside said annular contact portion, according to a radial direction orthogonal to the helix axis (L-L), - said closing flange is made of a sheet metal and is entirely formed by molding in a single piece.