Hydrogen sulphide (H2S) is colourless, hazardous malodorant gas produced mainly from biological effluent treatment facilities, petroleum refineries, textile industries, chemical industries, pulp & paper manufacturing units to the atmosphere. Short term exposure of low concentration H2S causes headache, skin irritation, nausea and can damage central nervous system if prolonged. High concentration inhalation can cause unconsciousness or lead to death. Keeping this in mind, sustainable and efficient practical technique to remove H2S gas is need of an hour. Geopolymers are aluminosilicate rich materials activated by alkaline materials. Geopolymers are capable of adsorbing contaminants from air, water, and soil. In this study, geopolymers prepared using fly ash & blast furnace slag are tested for H2S adsorption at ambient conditions. Geopolymers with three different sizes are employed as adsorbent material in up flow reactor and gas stream with 500 ppm H2S with N2 balance gas is passed through it at constant flowrate. Portable H2S sensor with logger was employed to analyze the H2S concentration in the effluent gas stream at 10 second interval throughout the experiment. The effect of particle size and ratio of fly ash & blast furnace slag on the H2S adsorption capacity was examined. Results indicate that geopolymers prepared using fly ash & blast furnace slag can effectively adsorb H2S directly from the gas stream at ambient conditions. Thus, fly ash and blast-furnace slag based geopolymers shall be promoted as sustainable adsorbent materials for H2S adsorption.