RFR HAZARDS TO THE SKIN

Guidance Curve for Potential Fueling Hazards

Permissible Exposure Time LimitsPartial List

Fire Controlman Volume 02-Fire Control Radar Fundamentals (Revised)
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strength of the field presents a biological hazard to personnel located at the point where the measurements were taken. PEL readings are the basis for determining RADHAZ safety boundaries. Permissible Exposure Time (PET)—This is the maximum time of exposure to a specific power density for which the PEL will not be exceeded when the exposure is averaged over any 6-minute period. Table 3-1 shows the PET for a variety of radars operated at their normal power levels. If you suspect that you or someone else has been overexposed to EMR, follow the flow chart in figure 3-2. If you confirm your suspicions, the exposure is considered an incident and must be reported as required by Protection of DOD Personnel from Exposure to Radio Frequency Radiation, DOD Instruction 6055.11. RFR HAZARDS TO THE SKIN.—The energy impinging on a person in an electromagnetic field may be scattered, transmitted, or absorbed. The energy absorbed into the body depends upon the dimensions of the body, the electrical properties of the tissues, and the wavelength of the RFR. Thus, the wavelength of the energy and its relationship to a person’s dimensions are important factors bearing on the biological effects produced by RFR. Significant energy absorption will occur only when a personal dimension is equivalent to at least one-tenth of a wavelength. As the frequency of radiation increases, the wavelength decreases and the person’s height represents an increasingly greater number of electrical wavelengths, increasing the danger from RFR exposure. As the frequency is decreased, the wavelength increases and the person becomes a less significant object in the radiation field. Thus, the likelihood of biological damage increases with an increase in radiation frequency. Also, as the radiation frequency increases and the wavelength becomes progressively shorter, the dimensions of parts and appendages of the body become increasingly significant in terms of the number of equivalent electrical wavelengths. When a person stands erect in a RFR field, the body is comparable to a broadband receiving antenna. 3-5 Figure 3-2.—Personnel RFR exposure decision chart.

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