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How to Check If Your Microwave Has a Radiation Leak

Want to know if your microwave oven leaks radiation? Here's a simple test.

Have you ever wondered if your microwave oven leaks radiation? If so, it turns out there is a pretty simple test to check the radiation seal on your microwave oven.

But, before we get into that, let's find out what exactly goes on inside one.  

How does a microwave cook food?

Have you ever wondered how that magical metal box in your kitchen heats up food and drinks? As it turns out, the process of "cooking" foods in a microwave oven is actually pretty interesting.

The secret comes from the namesake of the machine — microwaves. In case you unaware, these are a type of electromagnetic radiation (like light and radio waves) that lie towards the longer wavelength of the EM spectrum. 

diy microwave leak test
Source: Jimmy Tan/Flickr

Microwaves have frequencies ranging from about 1 billion cycles per second (1 GHz) up to 300 times that and have wavelengths (the distance between peaks) of between 12 inches (30 cm) and 0.04 inches (1 mm). To put that into perspective, radio waves typically have wavelengths varying from 1 mm to 100 km, and the light visible to our human eyes roughly falls between 380 to 700 nanometers (a sheet of paper is typically 100,000 nanometers thick).

Inside a microwave oven, microwaves are generated in a piece of tech called a magnetron and are beamed into the metal interior of the microwave oven. Here, anything you put inside the microwave oven (food or drink, etc) absorbs these rays. 

These microwaves excite the water molecules within the food/drink, causing it to heat up rapidly. The higher the water content inside the target food/drink, the faster they tend to cook, so that moist items cook a lot faster than more desiccated items. 

For bigger chunks of food, the microwaves actually only cook the outermost layers of the food, with the inner bits cooked via conduction of heat from the outside in. 

With all that radiation shooting around inside the microwave oven, it is obviously not ideal to have much of it leaking outside the box. For this reason, devices like microwave ovens must go through rigorous testing before they can be released for general use.

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How do your test your microwave for radiation leakage?

While very high standards are typically set for the tolerable levels of microwave leakage from microwave ovens, some microwaves can, and inevitably will escape. So, how do you test how effective the microwave shielding is on your microwave? 

As it turns out, there is actually quite a simple test. 

How to Check If Your Microwave Has a Radiation Leak
Source: Apoltix/Wikimedia commons

A fascinating, if not slightly disconcerting video by Physics Girl shows us why we should probably all check our microwave ovens. Her simple experiment shows us that there is an easy and effective way to check the integrity of the radiation shielding on your kitchen appliance. 

And all it takes is a little bit of lateral thinking. 

Microwave ovens, like cell phones, emit radiation in a specific band of EM frequencies -- specifically radio waves. All things being equal, you should expect that by placing your phone inside a microwave and closing the door the signal would be blocked by the shell of the microwave oven.

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If this is the case, it would also be reasonable to assume that you shouldn't be able to ring the phone once it is safely locked inside. 

It turns out, this is not actually the case. Somehow, and somewhere, EM radiation is able to reach the phone's antennae, resulting in you being able to call it from outside!

But how? 

As it turns out, the main form of shielding built into the microwave is a device called a "Faraday cage". These types of devices work dissipating the charge from EM radiation around their structure. This happens because electrons in the metal are excited by the radiation and move throughout the metal structure of the cage, creating an electric field that opposes and cancels out the external wave or field of anything inside it. 

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How to Check If Your Microwave Has a Radiation Leak
Source: Miya.m/Wikimedia Commons

In this sense, Faraday cages are effectively hollow conductors. Any breach in the structure of this cage can, theoretically, allow small amounts of EM radiation to "leak" inside (or outside) of the cage. 

According to this experiment, it appears this is indeed the case for some microwave ovens. 

Do all microwave ovens leak radiation?

This simple experiment is interesting, but it is not possible to quantify exactly how much leakage your microwave oven may have. For this reason, more sophisticated means of investigation are required.

For example, are all microwave ovens equal? Perhaps yours is of a lower quality than others? 

If you were to repeat the experiment using different ovens, as Physics Girl did, you will likely find that some do block the cellphones, while others do not. 

Building on her findings, she decided to find which part of the microwave was actually letting the radiation escape. Using aluminum foil to act as a near-perfect Faraday cage, she completely wrapped her phone. Sure enough, no one was able to call her phone. 

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does my microwave leak
Source: Tahir Hasmi/Flickr

The next step was to wrap certain parts of the microwave oven to narrow down and seek out the "leaky" parts. By systematically leaving parts of the microwave unwrapped they hoped to find the leak. It turned out that the door was the most likely culprit.

What are some other simple tests for microwave radiation leaks? 

To confirm her theory, Physics Girl employed the services of a self-professed hacker to make use of a HackRF radio transmitter and receiver to conduct a more sophisticated experiment. These devices can receive and transmit signals from 1 MHz to 6 GHz.

Using the device and a bona fide Faraday cage, they were able to demonstrate that you shouldn't be able to call a phone shielded by one — if it is fully intact.

Next, they tested whether commonly used Wi-Fi signals can get through the microwave's door. Wi-Fi signals use a similar frequency to microwave ovens so this is an interesting test. Microwaves typically operate at around 2.45 Gigahertz, whilst cellular signals tend to be around 1.9 Gigahertz or 850 megahertz.

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Sure enough, they were able to FaceTime the phone through the microwave door.

Interestingly, older microwave ovens have been shown to affect the quality of your domestic Wi-Fi routers and devices! But, we digress.

Using the same detector they were also able to directly detect microwave energy outside of the microwave oven as well.

leaky microwaves a problem
Source: Feral Indeed!/Flickr

They hypothesized that the radiation could be exploiting holes in the shielding of the door, allowing the microwave oven to leak radiation. As Physics Girl points out, her experiments show that some microwaves do let the specific frequencies of mobile phones through, providing clear evidence that some form of radiation leakage is possible within these appliances. 

Physics Girl does note that their experiment had a very small sample size, did not take into consideration the microwave oven's age or its proximity to a cellular tower.

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These variables could affect the results.

Should you be worried if you find that your microwave is leaking?

FDA regulations actually allow for a small amount of leakage over the lifetime of the microwave, of about 5 mW/cm2 at approximately 2 inches (5 cm) from the oven surface. The radiation itself is non-ionizing so won't damage your DNA directly, rather it will excite the water within your soft tissues. 

The FDA does warn that high exposure to microwaves can lead to a painful burn. Organs like eyes and testes are particularly vulnerable because they have relatively little blood flow to carry away the heat. Also, the lens of the human eye is very sensitive to heat. High levels of microwaves could cause cataracts.

The FDA also notes that this kind of damage would require a large amount of radiation. 

So, should you be concerned if your microwave oven leaks radiation? Put simply, no.

You are more likely to hurt yourself from a heated glass of water than the radiation itself. The radiation will not be in a high enough dose to cause you any harm. 

does my microwave leak
Leaking microwaves aside, never leave your Stormtrooper toys unattended near microwaves either. Source: DocChewbacca/Flickr

So, even if you discover that your microwave leaks some radiation, it is of such a small amount and a non-mutagenic kind, that shouldn't really lose sleep over it. Though, standing very close to your microwave at all times when it is in operation should probably be avoided.

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