Page "Microwave oven" Paragraph 18

Direct microwave exposure is not generally possible, as microwaves emitted by the source in a microwave oven are confined in the oven by the material out of which the oven is constructed.

Tests have shown confinement of the microwaves in commercially available ovens to be so nearly universal as to make routine testing unnecessary.

According to the United States Food and Drug Administration's Center for Devices and Radiological Health, a U. S. Federal Standard limits the amount of microwaves that can leak from an oven throughout its lifetime to 5 milliwatts of microwave radiation per square centimeter at approximately ( 2 in ) from the surface of the oven.

This is far below the exposure level currently considered to be harmful to human health.