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Abstract
The inclusion of a safety
interlock monitor is discussed. Additional safety provisions using an
interlock monitor are required for ovens manufactured after August 7, 1974.
The United States radiation safety performance
standard for microwave ovens, which was issued under the authority of the
Radiation Control for Health and Safety Act of 1968, is applicable to all. microwave ovens manufactured on or after October 6, 1971.
The standard was designed to protect the public from possible dangerous
exposure to microwave energy originating in microwave ovens by regulating
those performance characteristics which could lead to microwave leakage. It
is important to note that the "Act" only authorizes regulation of
performance and precludes regulation of design. While the standard contains a
number of protective aspects, two are paramount: (1) the limitation of
microwave emission from an operating oven, and (2) the requirement for two
interlock devices which must terminate generation of microwave energy upon
opening of the oven door, or in the words of the standard, "when access
to the cavity is possible."
During the interval between
publication and the effective date of the standard an event occurred which
raised serious questions about the adequacy of the two interlocks. The
resolution of these questions is the main topic of this paper. It is
appropriate, however, to examine some of the evidence of the adequacy of the
emission control aspects of the standard.
Between October of 1971 and
April of 1973, a
total of 349 ovens had been examined in the field and emission data
tabulated. The standard requires that oven emission not exceed 1 mW/cm² prior
to acquisition by the customer. The requirement is relaxed to 5 mW/cm² after acquisition
and remains so for the life of the oven. The chart, Table 1, summarizes the
emission findings.
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