Checking Ovens for Leakage
Reprinted from : http://www.fda.gov/cdrh/consumer/microwave.html
There is little cause for concern about excess microwaves leaking from ovens unless the door hinges, latch, or seals are damaged, or if the oven was made before 1971. In FDA's experience, most ovens tested show little or no detectable microwave leakage. If there is some problem and you believe your oven might be leaking excessive microwaves, contact the oven manufacturer, a microwave oven service organization, your state health department, or the nearest FDA office. Some oven manufacturers will arrange for your oven to be checked. Many states have programs for inspecting ovens or they may be able to refer you to microwave oven servicing organizations that are equipped to test ovens for excessive emission. A limited number of ovens are also tested in homes by FDA as part of its overall program to make sure that ovens meet the safety standard.
A word of caution about the microwave testing devices being sold to consumers: FDA has tested a number of these devices and found them generally inaccurate and unreliable. If used, they should be relied on only for a very approximate reading. The sophisticated testing devices used by public health authorities to measure oven leakage are far more accurate and are periodically tested.