Characterization of the Magnetic Fields Around Walk-Through and Hand-Held Metal Detectors

Abstract

Magnetic field strength measurements were made around eight hand-held and 10 walk-through metal detectors. The method was similar to that used in previous research for Electronic Article Surveillance units except a Cartesian rather than cylindrical coordinate system was used. Special magnetic field probes specifically designed for metal detector measurements were used. A non-metallic positioning apparatus was designed and fabricated. Magnetic field strength measurements were collected on one hand-held metal detector in the laboratory. The remaining data were collected at airport terminals, federal and state government buildings, and a local high school. Walk-through metal detectors had considerably higher magnetic field strengths [up to 299 Am(-1) p-p (3,741 mG)] than hand-held metal detectors [up to 6 Am(-1) p-p (76 mG)]. The frequencies of the magnetic field signal for walk-through detectors were between 0.1 kHz and 3.5 kHz while those for hand-held detectors were between 89 kHz and 133 kHz. Waveforms for all hand-held metal detectors were sinusoidal; those for walk-through metal detectors varied with most being saw-toothed or pulsed. Due to their higher field strengths and the pulsed nature of their magnetic fields, walk-through metal detectors likely pose a higher risk for medical device electromagnetic interference than do hand-held units. Root mean squared magnetic field strengths were calculated from the peak-to-peak values and compared to occupational and general public exposure limits. None of these limits were exceeded. Measurement repeatability was examined for one hand-held and two walk-through metal detectors. For the hand-held metal detector measurements at the location of the maximum magnetic field strength, measurements by three individuals had a repeatability (percent standard deviation) of 5.9%. Limited repeatability data were collected for on-site measurements of walk-through detectors. One unit showed repeatability of 0.1 to 4.5%; a multi-zone unit showed repeatability of 2.7 to 67.5%.

Effects of External Electrical and Magnetic Fields on Pacemakers and Defibrillators

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“…in light of increased security concerns. The variation between older and more modern arch and handheld detectors was demonstrated by Boivin et al6) More sophisticated software programs can discriminate between different implant metal alloys and discussions with airport security staff have revealed that varying lengths of implant can also be determined.…”

Fitness to fly for passengers with cardiovascular disease

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