How Microwave Ovens Work and Are They Safe

Since the 1970s, microwaves have become a common appliance in nearly every household. Almost as if by magic, these devices revolutionized cooking by heating and cooking food much more efficiently than their traditional counterparts, allowing users more time for leisure. 

From the beginning, microwave owners have used these time-saving appliances without any real knowledge of how they work. You put the food in, punch a few buttons, and an invisible force cooks or reheats the food in mere minutes. The mechanics sound simple, but the reality is anything but. 

If you have always wondered how microwave ovens work, keep reading as I explain how they work, the rules for using them, and the myths and facts behind these life-altering machines. 

How Microwave Ovens Cook Food

As their name suggests, microwave ovens cook food using a form of energy called microwaves. An electron tube inside the oven called a magnetron produces these microwaves, which are then reflected by the metal interior of the machine and absorbed by the food. Once the microwaves are absorbed by the food, water molecules inside the food begin to vibrate. This vibration produces heat, which ultimately warms and cooks the food. The more moisture content a food has, the faster it will heat in a microwave. 

I should note at this point that food cooked in a microwave is not ‘radioactive.’ Once the microwaves enter the food, it turns to heat, canceling the contamination factor. 

Although foods cooked in a microwave absorb heat directly, they do not cook from the inside out. Rather, the outside of the food heats via the microwaves while the center of the food cooks via the heat produced in its outer layers. 

Microwave Oven Lifespan

A microwave oven’s lifespan is about seven years with normal use. If it is used heavily to reheat leftovers, cook meals, or defrost frozen foods, it might only last four to five years, according to Mr Appliance out of Canada. The lifespan of a microwave oven may be further shortened by improper maintenance or placing the wrong items inside during operation, both of which may lead to irreparable damage or fire. 

Signs that it is time to replace a microwave oven include:

  • It takes longer for food to heat. Microwave ovens lose power over time. It can take longer and longer for food to heat than it once did. 
  • The door does not seal properly. The seal on a microwave oven is designed to contain the appliance’s low level of radiation. If the seal is compromised, radiation may leak out. 
  • The microwave is old. A microwave that is ten years and older is not as energy efficient as newer models. 
  • The appliance emits odd smells. An improperly maintained or malfunctioning microwave oven may emit odd smells such as burning, smoke, or sparks. If these smells are present, the appliance should be unplugged and repaired or replaced immediately. 

Microwave Oven Vs Conventional Oven

Although both microwave ovens and conventional ovens cook food, the two appliances are vastly different. 

First, microwaves are much easier to use. Food is placed inside, a timer is set, and in just a few short minutes, the food is heated and ready to eat. 

Second, microwave cooking is much faster than cooking in a conventional oven. This is because the food absorbs microwave energy directly, which heats the food rather than wasting energy heating the space around it. Also, microwaves do not need to be preheated as they cook from full power as soon as they are turned on. 

Next, microwave ovens are less expensive than their conventional counterparts. Basic models can be bought for less than $50 at most home goods retailers. These appliances also do not require any specialized installation, and they are cheaper to operate than traditional ovens. 

Finally, microwave ovens take up less space in the kitchen and are easier to clean. 

Are Microwave Ovens Safe

The short answer to this question is yes, microwave ovens are safe to use. The FDA’s Center for Devices and Radiological Health (CDRH) sets forth specific standards that all electronic products must meet. These standards ensure that radiation emissions are not harmful to the public’s health. 

With that said, there are a few rules users should follow when using microwave ovens.  

5 Rules for Using A Microwave Oven Safely

The FDA lists several tips for using a microwave oven safely

  1. Always follow the recommendations of the microwave’s instruction manual for operation, maintenance, and safety.
  2. Only use microwave-safe cookware.
  3. Stop using a microwave oven if the door is damaged in any way.
  4. Do not use a microwave oven that continues to operate when the door is open.
  5. Clean the inside of a microwave regularly using water, a mild detergent, and a soft cloth. Do not use any abrasive material such as steel wool. Special cleaners designed for microwaves are not necessary.  

Microwave Oven Radiation

Microwave oven radiation will heat human tissue the same way it heats food. Exposure to high levels of microwave radiation can cause burns, with the eyes and testes being the two most vulnerable areas of the body. These areas are especially susceptible to heat damage because they don’t have sufficient blood flow to carry away the excess heat produced by microwaves. For this reason, users should not lean against or stand too close to a microwave in operation, just in case. 

Microwave Ovens and Health Problem Myths

There are many myths and half-truths surrounding the safety of microwave oven use. Below, I go over a few of the most common to help users understand the truth. 


Despite the word ‘radiation’ being thrown around where microwave ovens are concerned, the appliance is not known to cause cancer, according to Although food cooked in a microwave oven absorbs microwave radiation, it does not become radioactive and thus does not cause cancer. 


In theory, cataracts can occur with the use of microwave ovens as the lens of the eye is especially vulnerable to intense heat. Having said that, the likelihood of this happening is rare since it would take an especially large amount of microwave radiation to cause this condition. 


When pacemakers were first used for cardiac patients, there was a concern about interference from a host of electronic devices including microwaves. Since then, pacemaker technology has advanced with today’s models protecting against such electrical issues. The FDA does not put warning labels on microwaves alerting to this concern, but if users have questions, they are encouraged to discuss them with their physician. 

Who Invented The Microwave Oven 

In 1946, a Raytheon engineer named Perry Spencer accidentally melted his snack while testing a magnetron. Upon discovering his melted peanut cluster bar, Spencer conducted another test of the magnetron. This time, he put an egg under the electron tube, which promptly exploded in his face within a couple of minutes. This accidental discovery led to the invention of the microwave oven.

The first commercial microwave, which cost nearly $2000 and weighed 750 pounds, became available in 1947. It was not a popular seller, and neither was the domestic version released in 1955. The invention was just too expensive and unknown at the time. 

Finally, the microwave oven caught on in 1967 with Amana’s version called the Radarange, and by 1975, a million microwave ovens were sold annually. Today, more than 90 percent of American homes include a microwave. 


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Andy has over 8 years of experience working on residential household appliances, performing diagnostics, and repairs across most major brands. He graduated from the Denver Institute of Technology, is NASTeC certified, and has worked for Mr. Appliance. Andy has contributed to features on major publications including Better Home & Gardens, Family Handyman, and