Why Microwave Catch Fire and What to Do When It Sparks

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Microwaves offer a quick and convenient way to heat food or prepare a quick meal. However, like any other electric appliances, microwaves run a risk of catching fire. Although microwaves are among the safest cooking appliances one can own, they can pose a fire hazard if not careful. Even the best microwaves can experience issues and catch fire.

Essential Takeaways:

  • Microwave fires usually happen due to overheated food, so keep an eye on the microwave as you cook.
  • Placing metals, such as aluminum foil or food packaging, inside the microwave could start a fire.
  • Electrical issues can also lead to fire hazards, such as power surges and shorted-out power supply units.

What Causes Microwave Fires?

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There are numerous reasons why a microwave oven can catch fire during use or even when not in use. Here are a few reasons why your microwave can catch fire:

A) Overheated food : According to Bob Schiffmann, a 50-year veteran of the microwave industry and president of the International Microwave Power Institute, microwave fires usually start for the same reason that oven or stovetop, or grill fires do: “It’s simply due to [the food] overheating.” A typical microwave does not cause smoke or fire on its own. However, if an ingredient becomes overcooked, it could begin to smoke and catch fire.

Food-based fires can also occur if someone overestimates or enters the wrong cook time. Schiffman further elaborated that food-based fires “create a lot of smoke, but they tend not to be all that dangerous because the components can’t catch fire.” In case you spot smoke or fire, turn off or unplug the microwave and keep the door closed. Moreover, UL-certified microwaves can contain small fires started by overheated food.

B) Metal and Packaging : Another common firestarter when it comes to microwaves are metal objects and packaging left inside the cavity as you cook. The rule is simple- do not put metal in your microwave, as any metal will spark in a microwave. Some of the metal objects that you should not place in the microwave are:

  • Pots and pans
  • Silverware
  • Plates, bowls, or cups with metal
  • Metal cans
  • Takeout containers with metal handles
    Avoid microwaving aluminum foil, a type of metal that is not safe to put in your microwave.

C) Putting plastic into your microwave : If you read that a bowl or plate is “microwave-safe,” you can place it inside the cavity without causing sparks or fire. Hence, it is best to double-check before putting something inside the microwave.
Some materials such as styrofoam, regular plastic wrap, and plastic containers can heat up, melt in the microwave, and start a fire. Like yogurt containers, do not microwave single-use containers, as they are not microwave-safe.

D) Using paper products : While some paper products are microwaveable, others will catch fire. So you should check if they are microwave-safe before putting them in the microwave.
Here are some of the products that you should check before microwaving:

  • Products like wax paper, parchment paper, and paper towels are safe if they have microwave-wave safe labeled specifically.
  • Recycled paper is not safe as it can have small pieces of metal in the paper.
  • Plain brown papers are also not safe for microwaving as they can catch fire
  • You should also avoid cardboard as they are unsafe for microwaves.

E) Microwaving grapes or chili peppers : Although it might sound odd, grapes and chili peppers will catch fire in the microwave. Grapes will spark in the microwave and can start a fire. Meanwhile, chili peppers contain capsaicin, which is flammable.

F) Putting non-food objects in your microwave : This might seem no-nonsense, but you should not put things like clothes, dry sponges, and electronic objects in a microwave. These objects can damage your microwave and might start a fire.

G) Using the microwave when there is no food inside : Running the microwave with nothing inside can cause severe damage to your appliance. As there is no food to absorb the energy, the microwave absorbs its own energy. Some microwaves can withstand this; however other microwaves can be severely damaged and catch fire.

H) Electrical issues : Some electrical issues can lead to microwave fires. If the supply shorts out, it could cause a fire. Occasionally, a power surge will turn the microwave on, causing it to run continuously until you shut it down, leading to a fire.

Why Do Microwaves Spark?

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Sparking in the oven cavity is not a sign of microwave malfunction, nor are they especially dangerous. Sparks and zaps occur because the energy waves that should be absorbed by your food instead bounce around between objects. As the energy gets concentrated in a small space, it reacts with something in the air or food, creating sparks.

Furthermore, metals with rough edges, like a ball of aluminum foil or fork, generally spark. Recycled papers might spark if they contain metal flecks. Meanwhile, some food packaging might contain hidden metal, and non-microwave-safe bowls and plates might also spark. Sparks inside the oven cavity are nothing to be concerned about.

Microwave sparks are plasma, which is the fourth state of matter. According to Aaron Slepkov, a Physics professor at Trent University in Ontario, plasma feeds off microwave energy. So if you glance up at the top of the oven cavity after you see the initial sparks, you might see plasma dancing around for the duration of the cooking time.

How to Avoid Microwave Fire

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  • Read the manufacturer’s guide : The manufacturer’s guide included with your microwave provides more information on microwave safety and what you should do and shouldn’t do.
  • Keep the area around the microwave clear : If the microwave vents are blocked, it will trap heat and start a fire. Also, make sure there are no objects near or up against the microwave and do not place things on top of the microwave.
  • Do not leave the microwave unattended : It is important to stay near the microwave if you heat meals that take longer than three minutes. The longer the food cooks, the more likely it is to burn or catch fire.
  • Check the directions before microwaving foods : If you are preparing food in the microwave, check the packaging before putting it in the microwave. Leaving the food in the microwave for too long can set it on fire. The packaging or the food box usually has directions placed on it.
  • Keep children away from the microwave : Children can turn on the microwave by mistake or unknowingly place dangerous things into a microwave. Therefore, it is better to place the microwave higher up so young children cannot reach it.
  • Do not use the microwave if the power cords are damaged : If something is wrong with your microwave’s power outlet it is plugged into, it could spark and cause a fire. So you should make sure all power cords and plugs are functioning properly and that the cord is intact.

FAQs

Why do vegetables spark in the microwave?

Microwaves produce an electric field when they operate, which can sometimes cause vegetables like peas, green beans, etc., to spark.

Are paper towels safe for use in a microwave?

Although paper towels are fine for use in a microwave, you should ensure they are not 100 percent cotton since they can catch fire.

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