Using adsorption locator for the most stable adsorption site searches, the authors investigated adsorption of mixture of gases with different carbon dioxide mole ratio at a single-walled carbon nanotube (SWCNT). A total of six mixtures were investigated, two mixtures consist of hydrogen, nitrogen and carbon dioxide with compositions 3:1:1 and 3:1:2. Whereas the remaining four mixtures consist of ammonia and carbon dioxide with compositions 5:1, 4:1, 3:1 and 3:2. Results demonstrated that gas interactions with carbon nanotubes increased as the mole ratio of carbon dioxide increased in H2, N2 and CO2 mixture, conversely decreased for NH3 and CO2 mixture. After increasing CO2 mole fraction from 1/5 to 1/3 for hydrogen, nitrogen and carbon dioxide mixture, adsorption energy and rate on carbon nanotube atoms increased by 45 and 33, respectively, due to a 59 increase in Van der Waal interactions. The preferred molar ratio of H2, N2 and CO2 mixture for adsorption is 3:1:2. The maximum adsorption energy and rate for NH3 and CO2 mixture is obtained using the 5:1 sample. Adsorption energy for the NH3 and CO2 mixtures increased by 18 when the ratio changed from 3:1 to 3:2 while the adsorption rate decreased considerably. © 2018 American Scientific Publishers. All rights reserved.