A burner nozzle is disclosed, comprising a nozzle body that includes a slit such that a line passage to the slit opens in an outlet face surface at the surface of the burner nozzle body. A plurality of channels is connected to the slit. A group of first channels is connected to a source of oxidizing substance, and a group of second channels is connected to a fuel source. Each of the first channels and second channels have a circumferential passage to the slit at a non-zero distance from the outlet face surface. Furthermore, each of the first channels and second channels is formed to output a directed tubular flow towards a side wall of the slit, or towards a circumferential passage in a side wall of the slit. A safe pre-mixed burner configuration is achieved. A burner and a surface treatment device incorporating the burner nozzle are also disclosed.