This research sought to determine the impact of humidity and the adsorption characteristics of CO, SO, SO2, NH3, and H2S on the surface of buckling bismuthene (b-Bi) adorned with Au for use in gas sensing applications. The density functional theory (DFT) including van der Waals dispersion utilized to investigate the gas sensing properties of environmentally friendly gases. All the gases exhibited physisorption except CO, which exhibited chemisorption. The Au-decorated b-Bi was found energetically stable and favorable due to its negative adsorption energy value. Moreover, the decoration of Au induces new states in the DOS and changes the nature of pure bismuthene to metallic. By adding Au to b-Bi, the CO gas's physisorption behavior transforms into chemisorption. According to the transmission results for CO and H2S gas molecules, these gases affect the system more significantly than SO, SO2, and NH3. Different famous properties were investigated in detail. Since the influence of humidity increases with an increase in adsorption energy, this type of material may continue to function even in the presence of humidity. This shows that the Au-decoration enhances the b-Bi potential for gas sensor applications.