Ackley and coworkers, 2003, proposed a review regarding the "Application of natural zeolites in the purification and separation of gases". "Patents and other literature have been surveyed to identify the bulk separation and purification processes for which" zeolites have potentialities. The results of the Ackley and coworkers' study is that "natural zeolites are particularly well suited for trace-gas removal. In contrast, they are less likely to provide competitive performance in bulk separations. Clinoptilolite and chabazite are judged the most versatile, while also offering unique adsorption characteristics. Effective and efficient methods for screening all types of adsorbents are presented for various gas separations. … The importance of including relevant process considerations in the analyses is demonstrated through application to processes for a bulk separation (O2 production from air) and purification (removal of trace levels of N2O from air). The results are not encouraging for the use of natural zeolites in air separation. Conversely, clinoptilolite and chabazite outperform commercially available synthetics in N2O removal from air" .