This study deals with nitrogen separation from carbon dioxide using hollow fiber membranes, having the ultimate objective of developing a hollow fiber membrane system for nitrogen generation from combustion exhaust gas. The membranes used were integrally asymmetric hollow fibers that were preferentially permeable to carbon dioxide, thereby resulting in a nitrogen enriched residue stream and a CO₂ enriched permeate stream. A laboratory scale hollow fiber membrane module containing 45 hollow fibers of 105cm long was used in the study to identify the best module configuration and flow arrangement. It was shown that, among all the module configurations studied, the best separation of CO₂ and N₂ was obtained if the feed gas flowed inside the hollow fibers and the feed gas and permeate flows were countercurrent. With a feed pressure of 300psig (2.07MPa gauge) and the permeate at atmospheric pressure, this bore side feed countercurrent flow configuration yielded a nitrogen productivity of 4.8sccm per fiber at a nitrogen purity of 98.5% and a recovery of 81% when a simulated dry combustion gas containing 18.3% CO₂(balance N₂) was used as the feed. This configuration was selected for use in the subsequent development of a full scale membrane module that comprised several hundred thousand fibers. Copyright (C) 2000 Elsevier Science B.V.