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Experimental work by others at 10 cm wavelength has shown that irreversible damage to the eye is caused by electromagnetic radiation, if the energy flux is in excess of about 0.2 watt/cm2. Intolerable temperature rise, due to total body irradiation may be anticipated for flux values in excess of 0.02 watts/cm2. Hence a discussion of hazards due to total body irradiation is of primary interest. This paper presents data which analyze the mode of propagation of electromagnetic radiation into the human body and resultant heat development. The two quantities which are considered in detail are: 1) coefficient, which characterizes the percentage of airborne electromagnetic energy as absorbed by the body, and 2) distribution of heat sources in skin, subcutaneous fat, and deeper situated tissues. It is shown: 1) The percentage of absorbed energy is near 40 per cent at frequencies much smaller than 1000 and higher than 3000 mc. In the range from about 1000 to 3000 mc the coefficient of absorption may vary from 20 to 100 per cent. 2) Radiation of a frequency below 1000 mc will cause deep heating, not well indicated by the sensory elements in the skin and, therefore, considered especially dangerous. Radiation whose frequency exceeds 3000 mc will be absorbed in the skin. Radiation of a frequency between 1000 and 3000 mc will be absorbed in both body surface and in the deeper tissues, the ratio being dependent on parameters involved.