When the PAT testing Code of Practice was updated in November 2012, the microwave leakage test was removed. The first reason for removal was because it was felt that PAT applied to the electrical safety of an appliance, whereas the microwave leakage test is secondary to the initial PAT test.
Secondly, this test should be carried out using the correct equipment. It was felt that there were too many low cost devices being used to measure microwave leakage that do not meet the required standard. The routine tests are defined in BS EN 60335-2-25:2002, for domestic microwave ovens, and in BS EN 60335-2-90:2002, for commercial microwave ovens.
The removal of the test from the Code of Practice does not mean it should no longer be carried out at all. A risk assessment should be undertaken to determine what testing is required and how often. This is especially important if you are using labels that specifically indicate the microwave has passed a leakage test.
What does the microwave leakage test involve?
The leakage test is designed to check there is no harmful radiation leaking from the appliance. This can happen if door seals are faulty, or if the shielding has been compromised in any way. By using a proper microwave leakage detector, you will clearly see if there is any dangerous leakage.
The test must be carried out while the microwave is in operation. It is important to note that the tester must be exactly 50mm away from the microwave during the test. A good leakage tester will have a spacer that ensures this distance is always maintained.
Microwave leakage is expressed as microwave power density in mW/cm2. Leakage should not exceed 5mW/cm2, sometimes expressed as 50W/m2, when measured at a distance of 50mm or more. The tester should be passed over the whole of the appliance, especially around the door seals, to check for leakage. If the result exceeds the recommend limit, the microwave should be removed from service and disposed of safely.
Assessing the heating power of a microwave oven
Having completed the microwave leakage test, it is good practice to check the heating power of the microwave. If the heating power is insufficient, this can result in food not being heated correctly which can in turn lead to health issues such as food poisoning.
- Fill the beaker with 1 litre of water at room temperature
- Measure the initial temperature of the water
- Heat the water in the microwave for 90 seconds on full power
- Stir the water briefly then measure the final temperature
Determine the rise in temperature as follows:
Temperature rise = Final Temperature – Initial Temperature
To calculate the heating power use the following calculation:
Microwave Heating Power (Watts) =
4190 x Temperature Rise
Heating Time (Seconds)
The result should be rounded down to the nearest 50W.
The following video from Martindale Electric demonstrates how to carry out the microwave leakage and heating power tests correctly. The Martindale TEK500 microwave leakage detector is designed to test for microwave leakage in accordance with the routine tests in the standards mentioned earlier in this article and has featured in previous editions of the Code of Practice.
The Martindale TEK500 is available to buy online as a complete kit, or standalone unit.
