A process for removing acid gas from a gas stream utilizes a low viscosity absorbent comprising a solution of at least one selected amine. The absorbent may include (1) at least one polyamine in the absence of an effective amount of tertiary amine functionalities having a pKa sufficient to neutralize carbamic acid, wherein the polyamine has at least one primary amine functionality having a pKa of <10.0 at 25.degree. C. and wherein the feed gas stream has an SO2 concentration less than 5 ppm vol.; or (2) a polyamine in the absence of an effective amount of tertiary amine functionalities having a pKa sufficient to neutralize carbamic acid, wherein the polyamine has at least one secondary amine functionality having a pKa for each sorbing nitrogen of <10.0 at 25.degree. C. The polyamines may include diethylenetriamine (DETA), triethylenetetramine (TETA) and tetraethylenepentamine (TEPA) or mixtures thereof.