October 14, 2010 10:02 AM   Subscribe

Is my microwave leaking radiation? Is it worth worrying about?

When we bought our home, our home inspector had a Device which he said showed that our microwave was leaking. It was a simple, pen-like thing with a light on the end of it and I think it made a ringing tone. My memory is that it looked a lot like the Thing you use to determine if an outlet is hot.

Anyway, he held up the Device around the outside edges of the microwave, and in one corner it lit up. And this test, apparently, showed that the microwave was leaking radiation.

What was the Device? And should we be concerned about using the microwave? Do we need to keep our distance?
posted by rouftop to Home & Garden (11 answers total) 1 user marked this as a favorite
Do you have a hole of 12 cm diameter (the approximate wavelength of the waves your oven uses) in the corner of your microwave? No? Then you have nothing to worry about.
posted by halogen at 10:04 AM on October 14, 2010

Microwave Oven Safety.
posted by blue_beetle at 10:08 AM on October 14, 2010

The thing he was using might be a WiFi signal detector. All consumer-grade E/M sources (microwave ovens, cellphones, cordless telephones, WiFi networks etc) operate in the same frequency band around 2.4GHz, so a signal detector (which is a rather simple piece of analog electronics) would pick up a leaky oven. In fact, poorly shielded microwaves are known as cause of interference in WiFi networks.

Along the same lines, I have heard of the following experiment for checking the radiation tightness of your microwave, but can't vouch for it: Put a working cellphone in it, close the door and use another phone to call it. If the microwave phone rings, it is an indication that 2.4GHz radiation can pass through. I wouldn't take it very seriously either way though, it's best to follow the advice given in blue beetle's link above.

Note: Do not microwave your phone while performing this experiment.
posted by Dr Dracator at 10:31 AM on October 14, 2010

Even if it is leaking the radiation from a microwave is not damagign to cell tissue at low exposure. If you don't hang out next to the microwave when it is running, and I mean right next to it, your exposure will be minimal. This is not the same kind of radiation as you get from plutonium or other gamma emitter and don't stress out about it. Chances are you get more exposure from talking on your cell phone (or even worse and cordless land line phone) than you will even get from even a badly leaking microwave oven. I mean how often is it on in your house? Mine is about 2 minutes a day average and I am not usually within 10' of it when it is on.
posted by bartonlong at 10:46 AM on October 14, 2010 [1 favorite]

Radiation is a scientific term which has a broad definition. In common usage, we think of things like X-rays and nuclear bombs. Those kinds cause cellular damage at the DNA level and lead to cancer and other diseases. This is ionizing radiation.

But radiation also includes things like visible light, infrared, and microwaves. These kinds of radiation, while they may warm you up, aren't going to cause cellular damage. This is non-ionizing radiation.

So no, I wouldn't worry about a bit of microwave leakage.
posted by sbutler at 10:52 AM on October 14, 2010 [3 favorites]

Did he test with a cup of water inside? Microwave oven leakage test devices (see eBay!) will respond to milliwatts. Most microwave ovens will leak more than that when operated with nothing inside. A proper test requires a cup of water.

Burns from radio wave absorption become a danger at a level of tens of watts. To avoid problems, don't rest your hand for long periods on the edge of the door when the oven is running. Instead, keep back an inch or two. (It helps to imagine that the edge of the oven door is very hot during operation. Keep hands away.)

To find leaks of significant wattage, you can pass a fluorescent tube along the edge of the door when the oven is running. If the tube lights up, you've got a major leak.
posted by billb at 10:53 AM on October 14, 2010

Replace it. Microwaves are dirt cheap and get significantly more effective all the time.
posted by Cool Papa Bell at 10:56 AM on October 14, 2010

> Do you have a hole of 12 cm diameter

Slots with length approaching 12/4 = 3cm are also a problem. They act just like a quarter-wave dipole antenna. That's the problem with door seals on microwave ovens. Look up "slot radiator"
posted by billb at 10:56 AM on October 14, 2010 [1 favorite]

You can (or used to be able to) get specific microwave oven leakage detectors— as Dr Dracator says, (domestic) microwave ovens and (most) wifi operate at the same frequency, 2.4 GHz, so a very simple wifi signal detector might also work for the same purpose. But I'm guessing your inspector's thingy was something like these.

A poorly-fitting door can leak microwave radiation. If the detector had to be near one corner of the door to light up, though, it's probably not leaking much at all, maybe no more than it's expected to in normal operation. Personally I wouldn't worry about it, from your description— the evidence that low levels of RF exposure (wifi, cell phones) can be harmful is tenuous at best and crackpotism at worst. (At high levels, of course, it can cook you; but you'd notice if that were happening. Feels a bit like standing in a sunbeam, I gather.)
posted by hattifattener at 3:29 PM on October 14, 2010

Run the microwave with something in it, and also place a cup of water near the suspected leakage area. If that cup of water increases in temperature, the leak is significant. If it doesn't, then you probably have more to worry about with your cordless phone.
posted by gjc at 4:29 PM on October 14, 2010

I think that's going a bit too far, gjc— it takes quite a bit of energy to raise the temperature of a cup of water perceptibly. Most organizations that set permissible exposure limits set the limit for 2.4 GHz RF at around 1 mW/cm2, which really isn't going to perceptibly warm a cup of water.

Admittedly that exposure limit is quite conservative. The FDA requires domestic microwaves' leakage to be under that limit but they can degrade to 5 mW/cm2 as they age. At ~27 mW/cm2 you may be able to feel the heat directly. Occasional exposure to even much higher levels is thought to be OK.

We really have no idea how much is leaking from rouftop's microwave, since it's easy enough to build an RF detector that will detect microwatts or less.
posted by hattifattener at 11:58 PM on October 14, 2010

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