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 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. One of these - IEC 60705, Household microwave ovens - Methods for measuring performance - has just been updated. It 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.

IEC have a number of international standards for microwave ovens. These include:

IEC 60335-1: Household and similar electrical appliances - Safety - Part 1: General requirements. This standard 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: Household and similar electrical appliances - Safety - Part 2-25: Particular requirements for microwave ovens, including combination microwave ovens, deals with the safety of microwave ovens for household and similar use.

IEC 61000-3-2: Electromagnetic compatibility (EMC) - Part 3-2: Limits - Limits for harmonic current emissions (equipment input current ≤16 A per phase). This standard sets limits for the harmonic current emissions from microwave ovens to ensure that they do not cause interference with other electronic equipment.

IEC 62301: Household electrical appliances - Measurement of standby power. This standard specifies methods for measuring the power consumed by appliances in standby mode, including microwave ovens.

All of these standards are covered by the IEC System for Conformity Assessment Schemes for Electrotechnical Equipment and Components. IECEE provides the assurance that tested and certified products meet the strictest levels of safety, reliability and performance as stipulated by the relevant international standards.

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