Two dimensional (2D) molybdenum disulfide (MoS 2 ) has an unique intrinsic influence on gas sensing applications. The effect of S and Mo vacancy creation increases the sensing nature of BBr 3 and SF 4 toxic gases. In this work, we have theoretically investigated the sensing capabilities and the electron transport behavior of armchair S vacancy (AmS-MoS 2 ), armchair Mo vacancy (AmMo-MoS 2 ), zigzag S vacancy (ZigS-MoS 2 ), and zigzag Mo vacancy MoS 2 monolayer with the highly toxic gases include of BBr 3 and SF 4 using first-principles calculations and Non-Equilibrium Green's Function (NEGF) theory. The optimal configuration indicates that there is a considerable change in the bond length and bond angle of BBr 3 andSF 4 gas molecules after adsorption. Among the devices, SF 4 adsorption on AmMo-MoS 2 and BBr 3 adsorption on ZigMo-MoS 2 shows enhanced adsorption energy of 0.9233 eV and 0.9987 eV, charge transfer of 0.111e and 0.233e respectively. The density of states, transmission spectrum, and I-V characteristic also show comparatively more changes after the adsorption of the gas molecule which reflects in the conductance and transport characteristic of AmMo-MoS 2 for SF 4 adsorption and ZigMo-MoS 2 for BBr 3 adsorption. All the results indicate that AmMo-MoS 2 and ZigMo-MoS 2 device shows beneficial results compared with the other devices. Hence, AmMo-MoS 2 and ZigMo-MoS 2 can be used for SF 4 and BBr 3 gas sensing applications.