[Show abstract][Hide abstract] ABSTRACT: This work presents results regarding electromagnetic shielding structures. The simulations were performed by using the finite difference time domain method, in which a sub-cellular formulation has been implemented for modeling thin steel walls. The implementation was validated via comparison of the obtained results to those available in the literature. Then, several geometries were tested, including apertures on the structures and the space between double shielding walls. Finally, a complete high-voltage laboratory was simulated (by analyzing the shielding efficiency).