Systems and methods of reducing outgassing of a substance within a reaction chamber of a reactor are disclosed. Exemplary methods include depositing a barrier layer within the reaction chamber and using a scavenging precursor to react with species on a surface of the reaction chamber. Exemplary systems include gas-phase deposition systems, such as atomic layer deposition systems, which include a barrier layer source and/or a scavenging precursor source fluidly coupled to a reaction chamber of the system.