Reports on three different kinds of paperm100% chemical pulp book paper, 60/40% mechanical/chemical pulp newsprint, and 100% cotton Whatmanmdeacidified by different aqueous and nonaqueous methods, and then treated to cause accelerated attack of air pollutants. Analyses capable of defining paper quality were carried out after various periods of exposure of samples to this polluting treatment. Paper that contains, as a result of deacidification treatments, a greater amount of alkaline salts consequently absorbs, under the conditions of the test, more acidic pollutants, which might be theoretically expected. Another result is quite surprising and requires a new assessment of deacidification: certain papers might, under the conditions of the test, suffer a greater deterioration of specific characteristics (degree of viscosimetric polymerization and the content of oxidized reactive groups as defined by the copper number) if deacidified than if not.