The first microwave was introduced at the end of World War II with the invention of radar technology. “Radarange” was first sold in 1946 but it was too large and too expensive for the general consumer. While many versions were introduced, it wasn’t until 1967 when the first countertop microwave oven was available for public use.

Built for long-term use, today’s microwaves are as safe as ever and conserve between 30 and 80 percent of the energy used by a conventional oven. Microwaves continue to be tested against strict criteria that include UL and federal safety standards. The tests, which apply to all UL certified ovens, check for radiation leaks, dielectric (voltage) withstand testing to detect any defect in the insulation system, and overheating of internal electrical components.

One potato, two potato…test!

Under the safety standard, each microwave is subjected to a “potato” fire containment test that simulates a fire in the oven cavity. As part of the test, one or more potatoes (depending on size and weight) may be placed inside the microwave (depending on its power or volume) and cooked until a fire starts. The goal is to help ensure that the fire stays inside the cooking area of the microwave.

To help prevent a potential fire from spreading, newer models may contain a thermal sensor that turns off the power before a fire spreads. The fan inside the microwave also provides added safety to keep internal components from overheating.

In addition to fire risks, consumers are often concerned about radiation exposure. As long as microwave door does not have any damage such as cracks or a broken handle, there is limited risk when standing in front of the microwave when it is in use. The door is designed with two interlocking switches that prevent microwave radiation from being generated until the door is closed properly, and the microwave will not turn on until the door is closed.

UL requirements follow the FDA standard that requires the emissions from microwaves (and other devices) at 5 milliwatts (mW) of microwave radiation per square centimeter for the upper limit, when measured two inches from the external oven surface. A 5mW of radiation per square centimeter is below the level that’s been shown to harm humans. At 20 inches away from the microwave, the amount of radiation would be only 1/100 of that value. So the further away you stand from the door, your potential exposure to radiation dramatically decreases.

An additional safety feature on the door is made up of an inner mesh-like screen with holes about 1 mm across to keep radiation in the oven cavity. This mesh allows users to look into the microwave oven without risking radiation exposure. If any of the safety features on the door are broken, buy a new microwave immediately to avoid any potential hazards.

Know how to use your microwave

Regardless of the size and power, microwaves have become a part of everyday life. Consumers should follow the manufacturer’s instructions when using their microwave, which include keeping it at a safe distance from the wall, only using microwave safe dishes, cooking smaller portions for more even heating/cooking,  and ensuring that metal is never inside when it is in use.


UL tests microwaves against many safety issues to help ensure that they work properly. As a reminder, this video reinforces why metal should not be placed inside the cooking cavity at any time.