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I have noticed that some people press the Stop or Pause button before opening an active microwave oven. Other people open them right up while they are running, without manually stopping them first.

Assuming that a microwave oven is operating properly, and that it was built in the last quarter-century, are there any real risks with opening a microwave oven without stopping it first?

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    Does the microwave keep running when you open it? I have never encountered one that would do that (I'm not actually sure they can do that) – YviDe Feb 14 '16 at 23:00
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    @YviDe They cannot, at least in the US. FDA regulations require dual interlock devices that shut the magnetron off when the door is opened. (Now watch this comment get deleted as an answer.) – Carey Gregory Feb 15 '16 at 5:14
  • @YviDe As Carey wrote, I think most (if not all) microwave ovens should stop when you open the door. But I don't know if, like a conventional oven, anything is released when you open the door without stopping it first. With a conventional oven, it's just heat. With a microwave oven, I don't know if more than heat is released. – RockPaperLizard Feb 15 '16 at 20:57
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    @RockPaperLizard Microwaves use radio waves to cook, and radio waves aren't something that can linger. Turn off that magnetron and there should be zero emissions present in nanoseconds, literally ages before the door can actually swing open. – Carey Gregory Feb 26 '16 at 0:25
  • @CareyGregory That's Carey, that's helpful. A little laugh at the "literally ages" term, but on this scale, that term could actually be appropriate! – RockPaperLizard Feb 26 '16 at 0:38
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There's nothing else to be released, because when microwave production is stopped the waves cease to exist.

From the FDA's FAQ about microwave safety:

systems that stop the production of microwaves the moment the latch is released or the door opened. In addition, a monitoring system stops oven operation in case one or both of the interlock systems fail. The noise that many ovens continue to make after the door is open is usually the fan. The noise does not mean that microwaves are being produced. There is no residual radiation remaining after microwave production has stopped. In this regard a microwave oven is much like an electric light that stops glowing when it is turned off.

Provided that your microwave meets regulations regarding the double locking mechanism, more radiation is leaked when the door is closed and the microwave is on than when the door is opened and the microwave is off.

  • Thanks neerajt. I think your last sentence is excellent, because it really puts it into perspective. – RockPaperLizard Feb 26 '16 at 0:36
  • @RockPaperLizard Is there some reason you never accepted it as an answer? – Carey Gregory Nov 5 '19 at 4:58
  • @CareyGregory I generally wait a while for additional answers, so as not to discourage other contributors. I think almost 4 years is sufficient! :) – RockPaperLizard Nov 5 '19 at 8:06
  • And the specific hazard if the interlock fails is radio burns: they're just like "grab a hot pan" burns, but they can form deeper in the body, rather than forming on the surface and extending inward. – Mark Nov 8 '19 at 0:45

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