Linear gas-burner with adjustable width

A linear gas and air burner comprising an air distributor tube (1) connected to a pressurized air supply (A), a gas distributor tube (2) located inside the air distributor tube and equipped with a gas inlet (21) connected to a pressurized gas supply (G), and at least one longitudinal row of gas injectors (5) extending radially from the gas distributor tube through air injectors (6) connected with air outlet apertures made in the wall of the air distributor tube, each gas injector (5) being connected to a gas outlet aperture (10) made in the wall of the gas distributor tube, wherein the gas distributor tube (2) is inwardly sealed by at least one sliding sealing body (36, 37, 66, 67) positionable so as to block the supply of gas to a desired section of the gas distributor tube, the at least one sliding sealing body is coupled with a control rod (41) extending longitudinally within the gas distributor tube and linked to control means (30, 31), for controlling the position of the at least one sliding sealing body, situated outside of the gas distributor tube, and all the air injectors (6) are continuously supplied with air even when the supply of gas to at least one of the gas injectors (5) is blocked by the at least one sliding sealing body.