How was microwave leakage discovered?
In 1945 the specific heating effect of a high-power microwave beam was accidentally discovered by Percy Spencer, an American self-taught engineer from Howland, Maine.
Employed by Raytheon at the time, Percy Spencer noticed that microwaves from an active radar set he was working on started to melt a candy bar he had in his pocket.
The first food deliberately cooked with Percy’s microwave was popcorn, and the second was an egg, which exploded in the face of one of the experimenters.
To verify his finding, Percy created a high density electromagnetic field by feeding microwave power from a magnetron into a metal box from which it had no way to escape.
When food was placed in the box with the microwave energy, the temperature of the food rose rapidly.
Raytheon later licensed its patents for a home-use microwave oven that was first introduced by Tappan in 1955, but these units were still too large and expensive for general home use. The countertop microwave oven was first introduced in 1967 by the Amana Corporation, which was acquired in 1965 by Raytheon.
A microwave oven, often colloquially shortened to microwave, is a kitchen appliance that heats food by bombarding it with electromagnetic radiation in the microwave spectrum causing polarised molecules in the food to rotate and build up thermal energy in a process known as dielectric heating. However microwave leakage can occur and should be regularly checked.
Microwave ovens heat foods quickly and efficiently because excitation is fairly uniform in the outer 25 – 38 mm (1 – 1.5 inches) of a dense (high water content) food item; food is more evenly heated throughout than generally occurs in other cooking techniques.
Direct microwave exposure is not possible because the micro waves come from the magnetron and are confined by the special material inside the microwave oven.
The second most important feature on a microwave oven is the redundant safety interlocks that remove power from the magnetron when the door is opened.
According to the United States food and drug administration centre for devices and radiological health, they limit the amount of micro waves that can leak from an oven throughout its lifetime to 5 milliwatts of microwave radiation per square cm at approximately 5 cm (2 in) from the surface of the oven. This is far below the exposure level currently considered to be harmful to human health.
The radiation produced by an oven is non ionising and therefore does not have the cancer risks that are associated with ionising radiation such as x-ray and high energy particles.
All microwaves sold have a protective interlock so that when the door is open the microwave cannot run its cycle thus putting a stop to the microwave radiation.
Microwave leakage only happens when there are food particles lodged in the interlocks, a crack in the seals or cracks in the metal casing around the oven.
At 250Rio we recommended that microwave leakage is checked on a yearly basis. Once the microwave passes the test a label with an asset code is placed on the side of the appliance. The results are recorded and then sent to the customer accompanied with certification.