EMI Threat Risk Assessment

FMS was engaged by the management of this landmark building in Manhattan to evaluate EMF conditions in an area of the Second Floor located immediately above the building’s main electrical switchgear. Shielding consisting of thick steel plates had been installed decades earlier on the floor slab of the Second Floor in an attempt to lower AC magnetic field levels in the area. However, prospective tenants for the Second Floor area consistently determined that the space was not desirable for office use, due to elevated EMF levels remaining in the space despite installation of the steel shielding. An EMF assessment by FMS confirmed elevated levels of AC magnetic fields throughout the subject area. FMS developed a cost effective plan to remove the inefficient thick steel plates and replace with a efficient shielding scheme utilizing highly permeable and conductive shielding materials designed to lower fields to acceptably lower values.

Replacement of the existing shielding by FMS was successfully completed in early 2009 on schedule and budget with minimal disruption to building operations.

AC magnetic field survey of the existing second floor space

An AC magnetic field survey by FMS of the existing Second Floor space confirmed the presence of AC magnetic field levels with peak values approaching 20 mG. The field survey measurement data documented the degree of shielding inefficiency provided by the existing multiple layers of thick steel plates mounted to the floor.

Computer simulation study of AC magnetic field emissions from First Floor main switchgear equipment

FMS developed a computer simulation study of AC magnetic field conditions throughout the Second Floor area from the building’s First Floor main electrical distribution switchboard to provide a “worst case” view of possible field levels without the presence of the exiting steel shielding. This computer simulation data was utilized to design a highly efficient shielding scheme.

Design of robust conductive magnetic field shielding schemes to mitigate EMI threat concern

The computer simulation study and site measurements provided sufficient data to enable FMS to design a highly robust shielding scheme which utilized both highly conductive and permeable shielding material to lower AC magnetic fields throughout the Second Floor under normal and future possible increases in electrical loading conditions to the building’s electrical switchgear.

Successful installation of shielding scheme

Views of the completed AC magnetic field shielding installation by FMS technicians on the Second Floor slab, structural columns and selected wall surfaces. The removal of existing heavy steel plate shielding and installation of replacement conductive and permeable shielding materials presented some formidable engineering and logistical challenges as the project required that disruptions to existing tenants in the building be minimized.

AC magnetic field measurements after installation of shielding

AC magnetic field spot measurements were recorded throughout the Second Floor after installation of the shielding to confirm that AC magnetic field levels had been comfortably reduced to the target lower levels