I try to keep up to date with what is happening on the web with anything to do with microwave ovens. A very motive subject is that of microwave leakage. I think it is very important firstly to describe as briefly as possible what microwaves are and how they work. A micro wave is exactly that, a very small wave of energy that is produced. It is very similar to a radio or mobile phone signal (in fact the correct term for those waves used in microwave cooking are radio frequency or RF waves). Instead of being converted by a receiver into a sound it is emitted into the microwave oven cavity where it is absorbed by the molecules of moisture in the food which in turn causes them to vibrate against each other. The friction this creates make the food hot. Microwaves therefore are Non Ionising. This means that they are not radioactive, they are not nuclear and they have no after life. If you open the microwave door during cooking the oven will stop producing microwaves and those in the cavity will have dissapated by the time you put your hand in the oven to remove the food. Their energy will have been completely converted into heat within the food.
If a microwave oven does leak into the atmosphere it is still unlikely to cause any great issues. From where they are emitted (the magnetron) their power reduction is inversely proportional. The power reduces greatly as the distance increases, therefore even if they did leak into the kitchen they would not have the energy or power to cause any harm in the kitchen.
A common rumour is that standing in front of the microwave whilst using it will be harmful. This is incorrect. Microwave ovens have many safety aspects to prevent just this. Their design means that microwaves cant escape during cooking. You may notice that all microwave doors are at least a certain thickness. This is because the edge of the door has a ‘channel’ built into it into which any stray microwaves will get trapped. The thickness of this channel allows the microwaves to then ‘fold up’ on themselves time and time again until they dissapate. The door screen that you can look through has a fine metal mesh built into it. This allows you to look into the oven but the holes are small enough not to allow any microwaves through. Often, if you feel around the doorway during cooking you can feel an flow of air. This is common and is not a flow of microwaves. Normal microwave design allows the cooling fan to blow air over the ‘workings’ of the oven to cool them, then through the cavity to carry away any condensation. there are some vents but a lot of air blows around the door frame beacuse there is a gap around the frame. Again the gap is not big enough to allow microwaves through. You will notice also that the oven has a metal outer cabinet. In the rare instances that a fault may occur inside the oven, any microwaves will bounce around underneath the cabinet antil they too dissapate. Occasionally this does happen and at worse those microwaves may damage the electronics on the control circuits. In our experience microwaves have never found an alternative exit from the oven.
As part of any microwave repair our engineers test the oven for any RF or microwave leakage. The test is quite easy but to be accurate we use a meter that is calibrated professionally on an annual basis.
Although we don’t find many problems with microwave leakage, it is useful for peace of mind to know that it is operating correctly and safely. If there is a liability issue involved for instance if microwave ovens are used by employees at work then good practice would be to have them checked periodically. As a business we can carry out periodic testing and apply a sticker to the oven to indicate the date of its last test.