Gas permeation membranes have a great potential in gas separation technology. In the recent years, there are many new membrane materials and new castingtechniques developed. High selectivity and permeability membranes have beingdeveloped by using these techniques ana all these cause separation by membrane becoming more feasible in the economical point of view. The objective of this research is to develop assummetric gas permeation membranes with different concentration of casting solutions. Experiments were carried out on eachof these membranes to obewerve the effect of different concentrations in thecasting solutions towards the membrane flux. Gas used in these experimentsis pure carbon dioxide, and membrane material is cellulose acetate. Membranes were casted with different polymer concentrations of 5%., 10%., 15%.,20%., 25% and 27% on weight basis. Only casting solution of 5% polymer was iunsuccessful to form membrane. Experiments were carreid out for each of themembranes with different feed pressure, ranges from 50 Psig to 150 Psig, andfeed temperatures from 25'C to 50'C. results gained come to a very importantconclusion that the highest permeability can be achieved by membranes formedfrom casting solution of concentration 20-25% polymer. Generally, membranesdeveloped in this research show that permeabilities will increase with theincrease of feed pressure and/or feed temperatures.