Theoretical investigations using density functional theory have been carried out to examine the interactions between armchair 4,4 gallium nitride nanotube (GaNNT) with NH3 (NO2) toxic gas molecule. Binding energy of NH3 and NO2 on nanotube surface lies within strong physisorption range. Mulliken, NBO and PDOS analysis suggests significant amount of charge transfer between molecular and nanotube fragments. The Transmission spectra evaluated through non equilibrium Green's function (NEGF) at different biasing voltage, across nanotubes are used to analyse the current voltage relationship. Further, the sensitivity of nanotube for NH3 and NO2 adsorption are validated through respective reduction and enhancement in conductivity. (C) 2016 Elsevier B.V. All rights reserved.