Gas turbine engine bearing chamber seals

A gas turbine engine sealing air supply system comprising a bearing chamber seal to prevent lubricant fluid loss from a fluid chamber, the sealing effected by ingress of sealing air. An air supply duct is coupled to the bearing chamber seal to provide the sealing air. A first duct is coupled between a starter air system of the gas turbine engine and the air supply duct to supply sealing air during gas turbine engine starting.