Report of preliminary measurements of electromagnetic radiation fields near microwave ovens, TSB No 5
Solem DL, Remark DG, Moore RL, Crawford RE, Rechen HJL · 1968
This 1968 study pioneered measurement of microwave oven radiation leakage, establishing early safety research precedents.
Plain English Summary
This 1968 technical report documented early measurements of electromagnetic radiation fields around microwave ovens, representing some of the first systematic research into microwave leakage from consumer appliances. The study was conducted during the early adoption period of microwave ovens in American homes, when safety standards were still being developed.
Why This Matters
This report represents a pivotal moment in EMF safety research - the recognition that consumer microwave devices could leak radiation into living spaces. Published just as microwave ovens were entering American kitchens, this work helped establish the foundation for current FDA leakage standards (5 milliwatts per square centimeter at 2 inches). What makes this particularly relevant today is how it demonstrates the pattern we see repeatedly: new EMF technologies enter the market first, safety research follows later. The reality is that microwave ovens still leak radiation within legal limits, and many units exceed standards as they age or sustain damage. This early research showed the importance of measuring actual exposures rather than assuming perfect containment - a principle that applies equally to today's 5G networks, smart meters, and WiFi systems.
Finding
A microwave oven from each of five different manufacturers was tested in an anechoic microwave chamber to determine the electromagnetic radiation exposures which would be encountered if safety devices failed. Commercially available instruments indicated power densities greater than 700 milliwatts per square centimeter at 30 em (12 inches) in front of an oven with the door open, and power densities of 10 niv/ome at 120 em (48 inches) from the ovens.
In their words
“A microwave oven from each of five different manufacturers was tested in an anechoic microwave chamber to determine the electromagnetic radiation exposures which would be encountered if safety devices failed. Commercially available instruments indicated power densities greater than 700 milliwatts per square centimeter at 30 em (12 inches) in front of an oven with the door open, and power densities of 10 niv/ome at 120 em (48 inches) from the ovens.”
Exposure Information
Specific exposure levels were not quantified in this study.
Study Details
To determine the levels of microwave energy to which people may be exposed if the safety devices on the ovens fail or are defeated, and to observe the response of three commercial microwave survey instruments when exposed to the microwave field emitted through the open door of an oven.
The microwave oven to be tested was placed in an anechoic chamber with the oven opening about 14 fee...
Power density measurements indicated that with interlocks defeated, power densities greater than 700...
The Federal Communications Commission has assigned frequencies of 13.56 + 0.007, 27.12 + 0.16, 40.68 + 0.02, 915 + 25, 2450 + 50, 5800 + 75 and 22,125 + 125 MHz to devices such as microwave ovens. Four of the ovens examined in this study operated at 2450 MHz, and one operated at 915 MHz. Survey instruments used for estimating microwave power or power density levels associated with oven operation must be designed and calibrated for at least the latter two frequencies. The three instruments have different types of antennae, and therefore differ in directivity, orientation sensitivity, effective antenna area, front-to-back ratio, efficiency, standing wave ratios, and useful ranges of sensitivity. Even when identically calibrated in the far field, one could not expect them to read identically under all conditions of exposure. When an open oven operating at 2450 MHz was used as the source of microwave radiation, the Hewlett-Packard power meter with dipole antenna indicated that microwave power levels decreased approximately as the inverse square of the distance from the door opening, from 30 to 300 cm. The dipole power reading taken with the dipole vertical at each location was added to that taken with the dipole horizontal. These sums were fitted to a smooth power function, and were found to fit the formula P = 0.09/D², where P was the sum of indicated powers in Watts, and D was measured in meters from the center of the plane of the oven door opening. The observations made at NCRH on microwave ovens operating at 2450 MHz demonstrated that power density levels which measured above 700 nW/cm² could be produced if the door safety devices failed or were bypassed. Under such conditions a separation of 4 feet between a person and the open door was often insufficient to bring the power density levels down to 10 nW/cm².
Show BibTeX
@article{report_of_preliminary_measurements_of_electromagnetic_radiation_fields_near_micr_g6355,
author = {Solem DL and Remark DG and Moore RL and Crawford RE and Rechen HJL},
title = {Report of preliminary measurements of electromagnetic radiation fields near microwave ovens, TSB No 5},
year = {1968},
}