Disclosed is a surface treatment device with a robust nozzle configuration. The device includes a nozzle for ejecting a primary stream of combustible substance to a gaseous atmosphere in an ejection direction; an ignition unit configured to ignite the primary stream in a point of ignition; and an impermeable shield providing a planar surface that is substantially opposite to the ejection direction and has in front of the nozzle a hole that allows passage of the primary stream. The shield is positioned between the nozzle and the point of ignition of the primary stream. The shield is advantageously dimensioned to allow simultaneous passage of the primary stream ejected from the nozzle and a circumferential secondary stream of gas from the gaseous atmosphere via the hole.