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I think I can smell the food inside my microwave. Is that bad?

I figured it's not necessarily unsafe, since you only need a cage to block the microwaves from escaping, but I'm not familiar with the precise architecture of a microwave oven.

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    Fwiw: I have an amazing sense of smell. I can smell things across the house; I have known that the food I put in the oven was ready by how it smelt. I have even detected a power fault problem with my nose (to be fair I suspected there was a fault but I didn't know for sure). I can certainly smell food in the microwave. Maybe an extreme example here but just thought I'd mention it: after all senses vary from person to person and it can be dramatic differences too. – Pryftan Feb 24 '20 at 22:30
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    you can boil vinegar and baking soda for a min or two to remove most odors. – dandavis Feb 25 '20 at 17:39
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    I have never not been able to smell food from microwaves; this is very common, IMO. – Incorporeal Logic Feb 25 '20 at 20:01

4 Answers4

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Microwave doors don't have an airtight seal; the window between the electronics and the cooking compartment is also not airtight, and the electronics are cooled by a fan. It would be surprising if some cooking smells didn't escape. In practice, every microwave I've ever had allows me to smell the cooking, from the very cheapest to some rather fancy ones with grill and convection.

This means that being able to smell the food cooking says nothing about the safety of the microwave, and you have no need to worry (unless there are other indications such as damage)

Chris H
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    It's worth noting that if you _did_ have an airtight seal on a microwave, you would also have a pressure cooker. Since microwaves are already supposed to be faster than a pressure cooker and this would require increasing the strength of the entire unit as well as adding pressure release valves, you can see why nobody would bother. – Turksarama Feb 24 '20 at 04:39
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    @Turksarama Also that would make opening it exciting. :-D – Kakturus Feb 24 '20 at 07:36
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    Microwave popcorn is something that comes to mind smelling a lot even when door is closed. – Viktor Mellgren Feb 24 '20 at 11:58
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    The metal screen embedded in the glass of the door is what is actually blocking the radio waves inside the oven. The size of the holes are calculated carefully to block the wavelength of the microwaves. The glass of the door is not technically needed, and you could just have a "screen door" and be just as safe. – JPhi1618 Feb 24 '20 at 20:01
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    @JPhi1618 safe for microwave radiation yes, but potentially very hot food splatter could exit there and burn people, or just mess up the floor and counter – Richie Frame Feb 25 '20 at 01:42
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    @RichieFrame It's also a pain in the behind to clean if there's no smooth surface encompassing it. – Mast Feb 25 '20 at 10:43
  • @RichieFrame, Oh of course - I wasn't meaning that the glass was pointless, just driving home the point that it doesn't need to be air tight. No "dangerous" microwaves get past the screen door, and glass is just to keep it clean and stop platters, etc. – JPhi1618 Feb 25 '20 at 15:05
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    @JPhi1618 the microwaves attenuate over around 5mm from the grille. Without the glass on the front, one could place a hand directly on the grille and receive a dose of microwaves into the skin. It could cause serious burns. – Tim Feb 26 '20 at 12:26
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    @JPhi1618that's not entirely true, the microwaves are blocked even by much larger holes. See https://www.youtube.com/watch?v=8bXhsUs-ohw – Adam Barnes Feb 26 '20 at 14:40
  • It's worth noting that microwaves are a type of [non-ionizing radiation](https://en.wikipedia.org/wiki/Non-ionizing_radiation). There is *not* a lot of scientific proof that this type of radiation can cause any harm. So even if the door was leaking microwaves, I wouldn't worry about it. – LeopardSkinPillBoxHat Feb 26 '20 at 21:27
  • @LeopardSkinPillBoxHat Your first sentence is true. Your second is true for low powers, but as high powers are generated, you have to quantify any leakage to quantify the risk. There's plenty of evidence for non-ionising radiation causing *thermal* damage at relevant powers, and you can replicate it yourself - just put a piece of meat the size of your hand in the microwave and press go! – Chris H Feb 27 '20 at 10:14
  • @ChrisH - yes the potential for thermal damage is there, but I guess the difference there is that you're probably likely to _feel_ any thermal damage and you could then avoid it. A bit different to ionizing radiation like X-Rays that you can't necessarily feel, but they can cause a lot of harm in sufficient quantities. – LeopardSkinPillBoxHat Feb 28 '20 at 03:05
  • @LeopardSkinPillBoxHat that's correct, but the potential to cause harm (that you dismissed in your earlier comment) is there – Chris H Feb 28 '20 at 08:44
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It's totally normal to smell the food in a microwave as they aren't meant to be sealed. Microwaves have fans to circulate the air and keep the electronics cool, so they will circulate aromas.

GdD
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  • There is no reason why a fan to cool the electronics would also cause air to flow through the oven's interior, the electronics are in a different part of the case separated by the wave guide cover. – Pete Kirkham Feb 24 '20 at 13:06
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    @PeteKirkham There is no point designing an airtight microwave-transparent seal between the electronics and the cooking compartment, because you also need to allow the excess pressure from steam to escape, and that will carry the cooking smells with it in any case. – alephzero Feb 24 '20 at 16:13
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    @PeteKirkham not for all microwaves I am sure, but mine has 1 fan, the magentron and power supply are cooled by this fan, and that is vented into the cooking area of the microwave, which then has passive vents on the opposite side, so 1 fan does all the work – Richie Frame Feb 25 '20 at 01:40
  • @alephzero allowing steam to escape into the electronics will significantly increase the risk of it failing due to corrosion and may cause creepage. It may depend on the fan to push the steam out another vent the other way from the electronics, but this is a compromise as some moisture will go against the flow once the fan is off, reducing the lifetime of the electronics. So maybe there is a reason for doing it - it's a bit cheaper and means the customer has to buy a new microwave every few years. – Pete Kirkham Feb 25 '20 at 18:31
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One element missing from other answers is how microwave ovens keep the waves inside. They use a Faraday cage https://en.m.wikipedia.org/wiki/Faraday_cage . The size of the holes you can have in those cages is related to the wave's frequency.

In the case of microwaves, millimeters-sized holes are ok. That allows the presence of a vent to let pressure, water vapor and smells out. In any case, if the inside was airtight, the door would blow open as the contents get hotter.

Jeffrey
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    You'll notice that most microwaves have a see-through mesh in the door, so yeah, it doesn't have to be solid metal all the way around. – Darrel Hoffman Feb 25 '20 at 15:20
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    Perhaps add the wavelength of the microwaves to your answer? [Consumer ones use about 2.45 GHz/12 cm](https://en.wikipedia.org/wiki/Microwave_oven#Principles) (120 mm). I don't know if quarterwave (3 cm/30 mm) would apply in this context or not. – Peter Mortensen Feb 25 '20 at 17:10
  • @peter not necessary. The holes are way smaller than what they'd need to be and as an explanation for people interested in cooking and not much physics, the technical bits would only be clutter. One can dig deeper and search for themselves about it if they are interested. – Mindwin Remember Monica Feb 26 '20 at 18:32
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A microwave does have a sealed door, and there are no fans blowing air out of the microwave. The cooling fan(s) are not connected in any way to the chamber where you cook food. Usually there are simply some venting holes above the door, usually not visible except from above, so you may not be able to see them if it is mounted high up. As other comments have said, this is necessary to keep pressure from building in the microwave.

These vents let any food smells out rather well.

one rad boi
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    my panasonic microwave actually does vent the fan into the chamber – Richie Frame Feb 25 '20 at 01:43
  • @Richie Frame: Mine too. – Peter Mortensen Feb 25 '20 at 17:05
  • I've used a variety of microwaves in the past, and I've even taken a fair number apart for their parts. Many of them have fans at the top for circulating the air within the chamber as well as venting, and very few have a rubber seal around the door. So, no, the doors generally aren't sealed and there are often fans in the cooking area. – computercarguy Feb 26 '20 at 17:20