There was a small fire in my microwave and it still works. Safe to use?
October 10, 2013 9:02 PM   Subscribe

A paper bag caught fire in our microwave and charred the insides while it was burning for about a minute. The microwave shut off during the fire, but now it seems to work normally. Safe to use?

My roommate's girlfriend was using a paper bag to make popcorn in our microwave (a trick she learned that apparently isn't always foolproof) and it caught fire and was burning for a minute or so before she noticed it. The microwave shut off by itself and we put out the fire.

The next day she attempted to clean the inside of the microwave, which was all black, and we tried turning it on. It seemed to work fine and heated some food normally

Safe to use? Potentially toxic or radiation spewing in some way?
posted by Defenestrator to Grab Bag (16 answers total) 1 user marked this as a favorite
The black stuff is polyaromatic hydrocarbons. It's not good for you to eat directly, but if you would eat barbecued meat or blackened fish, it's the same stuff.
posted by treehorn+bunny at 9:08 PM on October 10, 2013

Response by poster: Yeah, I'm not too worried about the persistent black coating which I recognize as just a good bbq charring, but I am worried about any potential damage which could make operation of the thing somehow unsafe.
posted by Defenestrator at 9:15 PM on October 10, 2013

For complicated reasons* I set my mother's microwave on fire about 15 years ago.

It is still running fine to this day and no one has suffered any ill effects. It did smell very bad for quite a while though.

*It involved drying green timber, which is quite do-able if you use the defrost setting and pay attention. Not so much if you forget it's in there for 20 minutes.
posted by deadwax at 9:29 PM on October 10, 2013 [1 favorite]

Radiation spewing: no. The plastic walls of the cooking chamber are meant to prevent you from accessing the guts of the microwave and to provide an easily-cleaned surface for soup to spatter against. The radio waves (which is what microwaves are) pass through those walls and hit reflective surfaces, and those reflective surfaces and the shielding in general is not compromised.

My only health concern would be any volatiles that came out from the charred plastic, and you'd get rid of those quite handily by changing the air in the microwave, which mostly happened when you opened the door last time. I don't *think* there's a danger of the soot warming up (during microwaving) and heating the plastic again, so I'd check that for heat after cooking something else (and check an unmarred surface for comparison) and then I'd stop thinking about it.
posted by Sunburnt at 9:57 PM on October 10, 2013 [1 favorite]

I accidentally set a microwave on fire recently, and the friend it belongs to is still using it with no problems.
posted by lollusc at 10:23 PM on October 10, 2013

If they're not obvious physical damage (ie melting), then I wouldn't worry about it.
posted by empath at 10:27 PM on October 10, 2013

I was about to write a long screed about how my family experienced a very similar thing and even checked in with the manufacturer(who had me take it to an "authorized service center") and it was fine... but honestly, why bother?

If it makes you uncomfortable, dump the freaking thing. My last two microwaves cost $5 and $2.50. The $2.50 special i have right now was a fancy "inverter" model from only a year or two ago that cooks all my food in like 20 seconds too. Go to goodwill and get the nicest, newest, cleanest looking one and either dunk this one in the garbage or look in to a local appliance recycling place.

I mean, unless you can't afford a new one why bother? they're so cheap that it's just not worth keeping a sketch one around.
posted by emptythought at 11:21 PM on October 10, 2013 [3 favorites]

An electrical item that has been involved in a fire? Toss it; as emptythought says, microwaves are cheap --- or put it another way: replacing it would be cheaper than risking a house fire!

But if you do decide to keep it, keep an eye on it --- don't turn it on and leave the room, only use it when you are right there to watch it. And consider leaving it unplugged when not in use.
posted by easily confused at 4:16 AM on October 11, 2013 [1 favorite]

Someone at my office set our microwave on fire and we were required to call the local fire department. (It was HILARIOUS.) The fire fighters told us to throw it out and get a new one as it couldn't really be safely used again. So, there's that.
posted by Aquifer at 4:46 AM on October 11, 2013 [1 favorite]

If the fire warped the microwave door or frame such that the door no longer seals perfectly, then the microwave should be replaced. If the plastic around the door is not distorted, then it's probably fine.
posted by ryanrs at 4:51 AM on October 11, 2013

You can smelt metal in a microwave, and provided you don't actually blow the thing up--which you can do pretty easily if you aren't careful--it's fine.

The only toxins are going to be from the blackening, which (1) you can probably remove if you really want to, and (2) are the same toxins on all the food you eat that's even a little bit charred, e.g., stuff on the grill.

The only real danger is that something has happened that's going to cause the thing to catch on fire for real at some point. Again, given the amount of abuse to which you can subject one of these things with no lasting ill effects, I'd say that's probably minimal.

If every person who ever set something on fire in their microwave always replaced it, microwave manufacturers would be making a lot more money than they are.
posted by valkyryn at 5:01 AM on October 11, 2013

I'd get a new one. They're super cheap now, and more energy efficient.

Why screw around?
posted by Ruthless Bunny at 5:43 AM on October 11, 2013

A fire caused by something burning in the microwave is a much different situation than a microwave that catches fire. In the latter case it's a no brainer to toss and replace. In the former as long as nothing is warped, melted or preventing the door from closing normally you'll be fine.

If your microwave isn't getting hot on the outside during use there is very little if any in the way of efficiency gains to be realized by replacement with a newer unit.
posted by Mitheral at 7:35 AM on October 11, 2013

My concern would be smoke and particles getting into the guts of the microwave, causing wear and tear on specific components, and aging all components in general a bit more quickly.
posted by ZeusHumms at 11:25 AM on October 11, 2013

Several years ago my wife wanted to turn on the timer on the microwave, but accidentally turned on the oven itself. With nothing inside to cook, the door of the microwave (the rubber seal around it) literally melted. There were holes in the door.

*That* was unsafe to use anymore.
posted by tacodave at 3:57 PM on October 11, 2013

the guts of the microwave, causing wear and tear

Meh. The magnetron is basically sealed, and most microwaves have few moving parts other than a wheel to direct the waves. This isn't like the fan question where you're possibly going to overheat the electrical supply either within the fan or your house walls.

I wish we had a photo to judge by.

My personal feeling is that a little bit of "browning" of plastic components is normal and harmless, but this doesn't happen within the component lifetime of modern microwaves. It did to the two nearly-identical Amanas my parents and grandparents bought in the 1980s, the latter of which became mine, and then ultimately replaced the former until it, too, died a couple of years ago.

But a fully blackened interior? Nah, not worth it. Probably smells bad as well. Ick. They're cheap now, get another. It may not have been substantially damaged, but it probably wouldn't pass a UL inspection anymore.
posted by dhartung at 4:23 PM on October 11, 2013

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