The safety of microwave ovens

It all started with a peanut bar. An engineer named Percy Spencer was visiting a lab where magnetrons - electron tubes for amplifying or generating microwaves - were being tested and the sweet snack in his pocket started to cook. He then put popcorn kernels near it and they exploded everywhere, a scene that was illustrated and used when he filed for the patents to use microwaves for cooking food in 1946.
Since then, microwave ovens have transformed the lives of many, though it hasn’t always been an easy ride. In the 1970s in the USA the market for microwave ovens took a plunge when the Consumers Union warned of uncertainty around radiation effects. But after much testing and the introduction of stringent microwave emission limits and safety requirements - as set out in the international IEC standards - these fears were largely abated.
High levels of safety and performance of microwave ovens are still required today and the standards for them are constantly reviewed to ensure they take into account any technological or market changes. The IEC standards for microwave ovens today include:
IEC 60335-1, which sets out the general safety requirements for household and similar electrical appliances,
including microwave ovens, and covers the safety requirements for the capacitors, such as their insulation and overvoltage protection.
IEC 60335-2-25, which deals with the safety of microwave ovens for household and similar use.
IEC 60705, which includes elements such as cooking and defrosting performance - tested on numerous different foods, ranging from raspberries to meatloaf - as well as power output and how to calculate the energy consumption of a cooking cycle, which is important for energy efficiency.

The standards are used as basis for design and manufacturing as well as conformity assessment of microwave ovens, such as for the International IECEE certificates offered by Nemko.

For more information, please contact Terje.Ulsrud@nemko.com

(This article is based primarily on an IEC blog from Sept.2024; edited by T.Sollie)