A valve for an extraction device of a molten metal or molten alloy atomizing chamber comprises a valve member which is rotatably mounted in a pipe. The peripheral edge of the valve member has a groove in which is located a rubber seal. A protecting member is located in the pipe upstream of the valve member with respect to the flow of an atomizing gas and metal particles through the pipe. The protecting member is positioned such that when the valve member is in the open position the protecting member is immediately upstream of the peripheral edge of the valve member to prevent metal particles impinging upon and wearing the rubber seal. The protecting member is also supplied with cooling gas and is arranged to direct the cooling gas through passages over the surfaces of the valve member to prevent the seal overheating.