An apparatus (1) for sealing an internal environment of a turbomachine, comprises a first chamber (2) connectable in fluid communication with a high pressure environment (HP) of a turbomachine (100) so that a working fluid can flow from the high pressure environment (HP) to the first chamber (2); a second chamber (3) in fluid communication with a lubrication circuit ( 106) so that a lubricant can flow from the lubrication circuit (106) to the second chamber (3); the first (2) and second chambers (3) are arranged in fluid communication with each other so that the working fluid can flow from the first (2) to the second chamber (3); a return line (4) for the working fluid in fluid communication with the first chamber (2) and connectable in fluid communication with a low pressure environment (LP) of the turbomachine (100) so that the working fluid can flow from said first chamber (2) to said low pressure environment (LP); a pressure regulating device (5) along the return line (4) configured to provide a predetermined pressure drop.