Gas sensing properties of pristine, defective and heteroatom substituted green phosphorene (GP) monolayers towards SF6 components such as H2S, SO2, SO2F2, SOF2 are investigated by using van der Waals corrected density function theory calculations. The adsorptions of H2S and SOF2 on pristine GP are found to be exothermic with weak binding energies (Eb) of-0.065 and -0.017 eV respectively, whereas the interactions of SO2 and SO2F2 are endothermic. We found that various vacancy defects and heteroatom substitutions enhance the Eb values of H2S, SO2, SO2F2 and SOF2 to -0.84, -1.04, -0.40and -0.73eV, respectively which are within desired range for efficient gas sensing applications. Presence of selected substituents (Al, B, C, S, Si) and vacancy defects result into measurable variations in electronic properties of GP upon the exposure of sulphur containing gases. We found that B- and S-doped GP systems show selectivity towards H2S and SO2, with Eb values of -0.57eV for H2S and -1.03eV for SO2. We believe that modified GP has potential to be used as excellent sensing material towards SF6 decomposition gases.