Benzene removal efficiency of granular activated carbon in indoor/poorly ventilated rooms has been studied. Commercially available coconut shell based granular activated carbon is used for this purpose. The benzene removal efficiency of carbon dosage of 50-100mg and benzene concentrations of 3-12 mu g at environmental parameters, viz. temperature (25-45 degrees C) and pressure (10-100 mbar) has been studied. Response surface methodology is used for the optimization of environmental parameters. The maximum percentage removal of 45-48 is achieved at 35 degrees C. It shows that the physisorption plays main role in benzene removal. The samples are analysed using GC.