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MEASUREMENT OF ELECTRIC AND MAGNETIC FIELD STRENGTHS FROM INDUSTRIAL RADIOFREQUENCY (15-40.68 MHZ) POWER SOURCES

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D. L. Conover, W. H. Parr, E. L. Sensintaffar, W. E. Murray, Jr. · 1975

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1975 NIOSH survey found 80% of workplace RF sources exceeded safety limits, revealing widespread monitoring failures.

Plain English Summary

Summary written for general audiences

This 1975 NIOSH study tested radiofrequency monitoring equipment and conducted preliminary workplace surveys of RF sources. The research found that at least 80% of industrial RF sources exceeded the safety field strength limits (200 V/m electric, 0.5 A/m magnetic) established in the 1974 ANSI standard. The study highlighted critical gaps in RF exposure monitoring techniques and the need for proper near-field measurement protocols.

Why This Matters

This foundational NIOSH research from 1975 reveals a troubling reality that persists today: widespread RF exposures exceeding safety guidelines in occupational settings. The finding that 80% of industrial sources exceeded established limits demonstrates how regulatory standards often fail to reflect real-world exposure conditions. What makes this study particularly significant is its focus on near-field measurements, which capture the magnetic field component that standard power density meters miss. This is the same type of exposure you experience when using devices close to your body. The research also exposed a critical regulatory gap that existed then and arguably persists now: the absence of comprehensive federal standards requiring proper field-strength measurements for the 10-300 MHz range, which includes many common RF sources. The scientists' concerns about 'totally incorrect RF exposure monitoring techniques' being widely used should give us pause about current exposure assessments.

Exposure Information

Specific exposure levels were not quantified in this study.

Cite This Study
D. L. Conover, W. H. Parr, E. L. Sensintaffar, W. E. Murray, Jr. (1975). MEASUREMENT OF ELECTRIC AND MAGNETIC FIELD STRENGTHS FROM INDUSTRIAL RADIOFREQUENCY (15-40.68 MHZ) POWER SOURCES.
Show BibTeX
@article{measurement_of_electric_and_magnetic_field_strengths_from_industrial_radiofreque_g5118,
  author = {D. L. Conover and W. H. Parr and E. L. Sensintaffar and W. E. Murray and Jr.},
  title = {MEASUREMENT OF ELECTRIC AND MAGNETIC FIELD STRENGTHS FROM INDUSTRIAL RADIOFREQUENCY (15-40.68 MHZ) POWER SOURCES},
  year = {1975},
  
  
}

Quick Questions About This Study

At least 80% of the radiofrequency sources surveyed exceeded the ANSI C95.1-1974 field strength guidelines of 200 V/m for electric fields and 0.5 A/m for magnetic fields, indicating widespread non-compliance with established safety standards.
Near-field measurements capture both electric and magnetic field components within fractions of a wavelength from the source. Far-field power density monitors miss the magnetic-field-induced power absorption that predominates in close-proximity exposures, leading to inaccurate assessments.
The 10-300 MHz frequency range had no federal personnel exposure standard specifying field-strength measurements, creating a regulatory gap that contributed to incorrect monitoring techniques and inadequate worker protection from RF radiation exposure.
The National Bureau of Standards (NBS) constructed and calibrated the radiofrequency electric and magnetic field-strength monitors specifically for near-field exposure measurements as part of this NIOSH research project on occupational RF exposures.
Personnel operating RF power sources receive near-field exposures because they work within fractions of a free space wavelength from the source. Standard far-field monitoring techniques fail to accurately measure these close-proximity exposure conditions.