How dangerous are the fumes from a microwave fire?

November 12, 2009 2:31 PM

How dangerous are the fumes from a microwave fire?

About ten minutes ago, someone tried heating up an aluminum travel mug in the microwave in our small, windowless office. I yanked the plug out once I noticed the a strange guttering sound and saw flames playing about the mug.

The fire died out once it consumed the available oxygen, and the person responsible contritely cleaned out the charred bits of plastic from the box and sprayed it with Febreze. Well and good.

But though we have the door cracked and a couple of fans going now, there's still a burnt tang in the air. Consulting Wikipedia, I got this: "When dielectric breakdown occurs in air, some ozone and nitrogen oxides are formed, both of which are unhealthy in large quantities."

What's "large quantities," exactly? Could our little dormitory-class microwave have produced that much before I pulled the plug? Any reason at all for worry here?

posted by Iridic to health & fitness (7 comments total)

No, I wouldn't think so.

It's not really any different than if any other kind of electronic device smokes. There isn't really anything magic about microwaves.
posted by Chocolate Pickle at 3:01 PM on November 12 [1 favorite]

Burning plastic (especially PVCs) contains dioxins, which are carcinogenic (source). It's hard to find neutral information about environmental toxins but dioxins do sound serious enough to where if it happened in my kitchen I'd purge the air by setting up an inflow fan and outflow fan in the windows and run it for about a day.
posted by crapmatic at 3:03 PM on November 12

It wasn't dielectric breakdown. The microwave didn't catch fire.

The aluminum got hot and burned the plastic parts of the mug, which caught fire.

The fire was no different than if you'd set it with a match. Just burning plastic, which isn't healthy, but isn't going to kill you from a single exposure of such small measure. Drinking pure dioxins? That might kill you. Working in a plastic foundry every day with no respirator? That'll eventually kill you.

But your little fire is not an issue, other than the smell being unpleasant.

As Chocolate Pickle notes: there's nothing magic about microwave ovens.
posted by Netzapper at 3:26 PM on November 12 [3 favorites]

When you have to spray febreeze into a microwave, it's time for a new microwave.
posted by 517 at 3:37 PM on November 12 [1 favorite]

Netzapper's answer reminded me that dielectric breakdown would have required pointed metal, or wire. The blunt curves of the mug didn't qualify, of course. [Smacks forehead.] Thanks for humoring my concerns, guys!

When you have to spray febreeze into a microwave, it's time for a new microwave.

It was, in fact, a new microwave. This is why we can't have nice things.
posted by Iridic at 6:20 PM on November 12

This probably goes with saying but I would do more than spray the inside of the microwave with Febreze. Febreze just traps odor molecules and toxins in cyclodextrin rings, it doesn't make the stuff disappear. I have no idea what happens when you microwave them. You should wipe that febreze off with some water so that whatever got deposited on the inside of the microwave doesn't end up in your food.
posted by Procloeon at 6:28 PM on November 12 [1 favorite]

This works well to remove the lingering odours inside the microwave itself: Set a bowl of diluted lemon juice (from real lemons) in there and nuke it several times.

Put 1 cup of water in the bowl. Add a couple of lemons, sliced. Run it for a couple of minutes, until the water boils, then stop the microwave and let it stand a couple more minutes. Carefully remove the bowl; wipe down all inner surfaces. Repeat one or two more times if necessary.

This helped us avoid a ridiculously high cleaning charge at a hotel once (and is also why we can't go to nice places.)
posted by Hardcore Poser at 9:04 AM on November 13 [1 favorite]