The BÃ 1\/4 chner flask can also be used as a vacuum trap in a vacuum line to ensure that no fluids are carried over from the aspirator or vacuum pump ( or other vacuum source ) to the evacuated apparatus , or vice versa . The BÃ 1\/4 chner flask can also be used as a vacuum trap in a vacuum line to ensure that no fluids are carried over from the aspirator or vacuum pump ( or other vacuum source ) to the evacuated apparatus or vice versa .