Boiler for the heating of fluids, comprising: - at least one combustion chamber; - burner means of at least one first combustible fluid and substantially aeriform and at least one second comburent fluid and substantially aeriform to obtain at least one third combustion fluid substantially aeriform, said burner means being associated with said combustion chamber and comprising: - at least one burner of the non-premixed type; - at least one fan element suitable for the movement of said second comburent fluid; - at least one first duct, connected to said fan element, in which said second comburent fluid circulates; - at least one flame ignition device, and revealing the presence of the flame itself, due to the combustion between said first combustible fluid and said second comburent fluid; - at least one second duct in which said first combustible fluid circulates; and - adjusting means of said first combustible fluid; - heat exchange means arranged inside said combustion chamber, said third combustion fluid lapping said heat exchange means for the heating of a fourth thermal carrier fluid; characterized in that said burner comprises: - at least one first injector body substantially hollow comprising a passage channel connected to said second duct, said first injector body comprising a plurality of passage holes connected to said passage channel and suitable for the dispensing of said first combustible fluid; - at least one second body substantially hollow associated on top of said first injector body and able to define a mixing area of said first combustible fluid and of said second comburent fluid to obtain said third combustion fluid; and - at least one recirculation element of said second comburent fluid arranged in the proximity of said passage holes, said recirculation element comprising a plurality of grooves inside which said second comburent fluid flows. - at least one combustion chamber; - burner means of at least one first combustible fluid and substantially aeriform and at least one second comburent fluid and substantially aeriform to obtain at least one third combustion fluid substantially aeriform, said burner means being associated with said combustion chamber and comprising: - at least one burner of the non-premixed type; - at least one fan element suitable for the movement of said second comburent fluid; - at least one first duct, connected to said fan element, in which said second comburent fluid circulates; - at least one flame ignition device, and revealing the presence of the flame itself, due to the combustion between said first combustible fluid and said second comburent fluid; - at least one second duct in which said first combustible fluid circulates; and - adjusting means of said first combustible fluid; - at least one burner of the non-premixed type; - at least one fan element suitable for the movement of said second comburent fluid; - at least one first duct, connected to said fan element, in which said second comburent fluid circulates; - at least one flame ignition device, and revealing the presence of the flame itself, due to the combustion between said first combustible fluid and said second comburent fluid; - at least one second duct in which said first combustible fluid circulates; and - adjusting means of said first combustible fluid; - heat exchange means arranged inside said combustion chamber, said third combustion fluid lapping said heat exchange means for the heating of a fourth thermal carrier fluid; - at least one first injector body substantially hollow comprising a passage channel connected to said second duct, said first injector body comprising a plurality of passage holes connected to said passage channel and suitable for the dispensing of said first combustible fluid; - at least one second body substantially hollow associated on top of said first injector body and able to define a mixing area of said first combustible fluid and of said second comburent fluid to obtain said third combustion fluid; and - at least one recirculation element of said second comburent fluid arranged in the proximity of said passage holes, said recirculation element comprising a plurality of grooves inside which said second comburent fluid flows.