Is Microwave Oven Radiation Safe?

What are Safe Levels of Microwave Oven Radiation?

 Microwave Countertop Oven Radiation

Microwave Countertop Oven Radiation

We will examine the Safe Levels of Microwave Oven Radiation coming from both built-in and countertop Microwave ovens. Microwave ovens are sealed enclosures that heat food or liquids by means of exciting the water molecules in them  to such an extent that they heat up. Power in a microwave oven can often exceed several thousand watts.  Very little of this microwave radiation escapes to the external surfaces and areas in close proximity to  the oven, because these ovens  are normally adequately shielded.

The amount of power density in air is defined by the power produced, divided by the volume in which that power exists;  For example, watts/cubic inch, or watts per cubic centimeter.  The U.S. Food and Drug Administration (FDA) defines the external safe limits in terms of milliwatts per cubic centimeter. They also define the frequency of microwave radiation in these appliances, to be in the range of  890-6000 Megahertz.  This frequency band is sometimes called the ISM band, and is the same band used by cell phones , portable phones, and  computer Wi-Fi equipment.

FDA Definition of  Safe Levels of Microwave Oven Radiation

The FDA defines the  safe level of microwave energy (at the time of customer purchase)  to be less than one (1) milliwatt per square centimeter at a any point distant from the the external surface of the oven.  This  limit is increased to a maximum of five (5) milliwatts per square centimeter over the lifetime of the oven.

All microwave ovens are required to be designed with safety interlocks that will shut off the microwave energy if the door is opened while the oven is in operation. If the oven ever operates with the oven door open, unplug it, discontinue its use, and then take it to a repair center as soon as possible.

How Do I Know if  My Microwave Oven Radiation is Within the Safety Limits?

Since unsafe levels of microwaves can only be measured by means of power devices that are designed for this purpose.  A microwave oven tester can be obtained to measure these values. When using the tester the oven should be filled with a glass of water. Put into the glass about 300 milliliters of water. Turn the microwave oven up to its maximum heating setting (if this is possible), and run it while you make your measurements. The water acts as a load, and simulates food or other liquids that you typically would be heating.  Microwave ovens should not be operated without some food or beverage in them. If they have nothing to heat, the emissions out of the oven will typically be quite a bit higher, and it will not be good for the longevity of the oven.

Test Instruments Can Check Microwave Oven Radiation

Moderately priced instruments for oven radiation testing are available for the consumer market.  A Microwave Oven  Radiation Tester will determine if your oven is leaking too much microwave energy.  The maximum “safe level” as mentioned earlier is five milliwatts/cubic centimeter.  This is a Power per unit Volume measurement, (milliwatts per centimeter-squared)  and these testers will measure this power density during a test.  Recommended testing techniques sometimes include placing the tester in close proximity to the joints around the front door, and around the sides of the unit. Some testers will sound an alarm, or perhaps flash a signal or LED, if the tested value is over the recommended limit. If the alarm should sound or the level exceed the recommended power limit, the unit should not be used further, and should be returned to the vendor, or taken to a service shop.

Microwave Ovens Originally Called “Radar Ranges”

Microwave ovens were originally called Radar Ranges. The radar designation came from the WWII military term for microwave or UHF radio waves that were used to determine the distance of enemy aircraft and ships at sea. The acronym became RADAR, “radio detection and ranging.” In order to use this radar ranging technique,  powerful UHF microwave transmitters were developed.  In the process of accomplishing this task, it was found that microwave transmitters were able to heat water molecules in other substances that largely consisted of water.

Early WWII Radar Dish

Early WWII Radar Dish

After the War, it was discovered that Radar waves could heat other items as well. The idea was born when it was discovered that it could be used for rapidly heating food and beverages.  In the  early post war era, these microwave transmitters were designed to fit into sealed cabinets called “radar ranges”.  Later on the term “Radar” was dropped, presumably because of its connection to the War, and to steer public discussion away from the known cases of radar damage caused in humans by accidental exposure.  A number of  incidents occurred resulting in death or  serious  burns  inflicted on humans, most accidents of this type occurred in the military services. Some accidents still tend to occur when users attempt to fix their own microwave ovens, without heading the warnings that High Voltage lurks within the cabinet!


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