An improved method of operating an apparatus for making acetic acid of the class including a production system having a reactor containing a reaction medium and a product purification train wherein the production system is vented to an absorber tower, the improvement comprising: (a) carbonylating methanol or reactive derivatives thereof in the reactor in the presence of a Group VIII metal catalyst and a methyl iodide promoter while maintaining a concentration of water in the reactor of from 1-10% by weight of the reaction medium and concurrently maintaining in the reactor a predetermined partial pressure of carbon monoxide; (b) venting non-condensables from the production system so as to provide low pressure vent gas only; (c) feeding the low pressure vent gas from the production system to the absorber tower, the vent gas including methyl iodide and optionally additional volatile components, the absorber tower adapted for receiving the low pressure vent gas stream and removing methyl iodide therefrom with a scrubber solvent, the absorber tower also being coupled to first and second scrubber solvent sources which are capable of supplying different first and second scrubber solvents and further comprising a switching system for alternatively providing first or second scrubber solvents to the absorber tower from either the first scrubber solvent source or the second scrubber solvent source; (d) wherein the carbonylating methanol or reactive derivatives thereof in the reactor is in a start-up or transient operational state, supplying the first scrubber solvent to the absorber tower, the first scrubber solvent consisting essentially of acetic acid; wherein the carbonylating methanol or reactive derivatives thereof in the reactor is in a steady state, supplying the second scrubber solvent to the absorber tower, the second scrubber solvent comprising methanol, methyl acetate or mixtures thereof; (e) contacting the low pressure vent gas with the first or the second scrubber solvent thereby removing methyl iodide and optionally additional volatile components from the gas and absorbing methyl iodide and optionally additional volatile components into the scrubber solvent; and (f) feeding an absorber return stream including the first scrubber solvent and absorbed methyl iodide and optionally additional absorbed volatile components to a light ends column and/or a dehydration column of the purification train, or feeding an absorber return stream including the second scrubber solvent and absorbed methyl iodide and optionally additional absorbed volatile component to the reactor. (a) carbonylating methanol or reactive derivatives thereof in the reactor in the presence of a Group VIII metal catalyst and a methyl iodide promoter while maintaining a concentration of water in the reactor of from 1-10% by weight of the reaction medium and concurrently maintaining in the reactor a predetermined partial pressure of carbon monoxide; (b) venting non-condensables from the production system so as to provide low pressure vent gas only; (c) feeding the low pressure vent gas from the production system to the absorber tower, the vent gas including methyl iodide and optionally additional volatile components, the absorber tower adapted for receiving the low pressure vent gas stream and removing methyl iodide therefrom with a scrubber solvent, the absorber tower also being coupled to first and second scrubber solvent sources which are capable of supplying different first and second scrubber solvents and further comprising a switching system for alternatively providing first or second scrubber solvents to the absorber tower from either the first scrubber solvent source or the second scrubber solvent source; (d) wherein the carbonylating methanol or reactive derivatives thereof in the reactor is in a start-up or transient operational state, supplying the first scrubber solvent to the absorber tower, the first scrubber solvent consisting essentially of acetic acid; wherein the carbonylating methanol or reactive derivatives thereof in the reactor is in a steady state, supplying the second scrubber solvent to the absorber tower, the second scrubber solvent comprising methanol, methyl acetate or mixtures thereof; (e) contacting the low pressure vent gas with the first or the second scrubber solvent thereby removing methyl iodide and optionally additional volatile components from the gas and absorbing methyl iodide and optionally additional volatile components into the scrubber solvent; and (f) feeding an absorber return stream including the first scrubber solvent and absorbed methyl iodide and optionally additional absorbed volatile components to a light ends column and/or a dehydration column of the purification train, or feeding an absorber return stream including the second scrubber solvent and absorbed methyl iodide and optionally additional absorbed volatile component to the reactor.