As a result of the enormous increase in mobile phone usage throughout the world, mobile phone base stations are located in almost everywhere nowadays. Many scientific studies have investigated possible health symptoms of mobile systems radiation. The globally recognised organisations have started to release maximum radio-frequency (RF) exposure levels that are regarded as safe. An efficient approach to decrease the RF exposure levels inside the buildings is to transform building walls to a frequency selective surface which filters out global system for mobile communication signals but allows the others, such as radio and television signals. This study proposes a new frequency selective surface element geometry which leads to a minimum 20 dB attenuation in 900, 1800 and 2100 MHz mobile communication bands according to Swiss electromagnetic radiation prevention limit values (NISV, 23 December 1990). High-frequency structure simulator software is used for simulation and design purposes. Due to a given good insight into the resonance characteristics of the FSS structures, it is benefited from the equivalent circuit model in the optimisation process. Achieved results show that the proposed FSS element geometry has a stable frequency response with minimum 20 dB of attenuation levels for transverse-electric (TE) and transverse-magnetic (TM) polarisations when the angle of incident wave is varied from 0 degrees to 60 degrees.