Why microwaves can burn - and how to use your microwave safely (2023)

Almost any cooking appliance can emit smoke or catch fire, and few blame their hob, oven or toaster for these kitchen mishaps. But when a microwave sparks or glows, it seems to trigger a deeper sense of fear and dread.

In fact, microwave ovens are among the safest cooking appliances you can own. When they start to burn, it's mostly for the same reasons as any other electric oven. (Well, a microwave oven is the only appliance where you can accidentally do thisKugelblitz, but it's not that big of a deal as it turns out.) Here's what you need to know.

The main culprit is overheated food or packaging

According to Bob Schiffmann, a 50-year microwave industry veteran and President ofInternational Institute for Microwave Energy,1Microwave fires usually start for the same reason as oven, stovetop, or grill fires: "It's just overheating of the food."

Food fires in the microwave almost always result from someone overestimating the cooking time or entering it incorrectly. An extra three minutes can mean the difference between a nice baked potato and a charred, smoked mess. Also, blasting a skinny kitchen that you think is frozen but is actually more like room temperature can cause problems. Another culprit can be packaging caught on the side of the machine near the wave emitter - such as a large bag of popcorn pressing against the walls of a small oven as the kernels expand.

Schiffmann said food fires like this "create a lot of smoke, but aren't usually that dangerous because the ingredients can't actually burn." If you notice smoke or fire in the cooking cavity, turn off the microwave or unplug the power cord, and leave it alone But you closed the door. UL-certified microwave ovens (which are almost all) areDesigned to contain small firesIt starts with ordinary foods (like popcorn or potatoes), so it should be safe to leave the microwave alone while the flames die down.

Other types of fires are not as common

Schiffmann said he knew of three other ways dangerous microwave fires can start: 1) the power supply can short out and burn the components in the house (this is a risk with all electrical equipment); 2) A power surge can trick the microwave into turning on, and it can run non-stop until someone notices and turns it off (that exists).reportsof thishappenswithmultiple brands); 3) A part of the stove may ignite if overheated (e.g.these whirlpool models).

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Microwave ovens have built-in safety features to reduce the risk and severity of these types of fires. They also don't seem to be nearly as common as foodborne fires: A representative from the National Fire Protection Association told us that 17 percent of microwave oven fires originate inside the appliance (which is consistent with non-foodborne fires ). However, there is always a risk and it is important to follow the safety instructions in the manual to prevent any of these risks from occurring.

Unfortunately, you don't know if your microwave is particularly susceptible to these types of fires until you see it happen or there's a class action lawsuit and recall.

Sparking can occur, which is not really a concern

According to Aaron Slepkov, a physics professor at Trent University in Ontario, pops and sparks in the oven cavity are not a sign of a microwave malfunction and are not particularly dangerous.

Sparks occur because the energy waves that should be absorbed by your food bounce between objects instead. The energy is concentrated in a small area so it tends to react with something in the air or food and create a spark.

Metal with rough or sharp edges, such as a fork or aluminum foil ball, will almost always cause a spark. Paper towels made from recycled materials may also (unintentionally) contain metal stains that can create sparksNational Health Institute. It is not easy to imagine that some food packaging could also contain hidden metal. Even non-microwaveable bowls and plates can crackle or spark.

And under the right conditions, food can also create sparks.Grapes are the most notorious culprit(video), and Slepkov co-wrote one of themPapierwho investigated this phenomenon (his laboratory was nicknamed the "Grape Balls of Fire" project). Grapes are the ideal size and moisture level for sparking, but the same can happen with peas, blueberries, and other foods.

If you see sparks in the furnace room, don't worry - they're like fireworks for geeks. Microwave sparks are a plasma, the fourth state of matter, which is much rarer on Earth than gases, liquids or solids. According to Slepkov, plasma is formed from microwave energy. If you look up into the oven chamber after seeing the first sparks, you can see the plasma dancing around throughout the cooking time. "It's literally ball lightning," Slepkov said (although some expertsclaims it's not quite the same).

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Given enough time and sparks, the plasma can char the top of your oven and reflected microwaves can damage the magnetron (the core component of the oven that creates the waves that heat your food). But according to Slepkov, the danger of an inferno is low. The plasma will not burn your food as it flows to the top of the cavity. "It won't explode your microwave or anything. And if it damages your microwave, it will only damage your microwave enough to immediately stop supplying that plasma.”

Microwaves are fairly safe as cooking appliances

One fire is too many, but the numbers suggest microwaves are fairly safe.discretioncapablevary, but at least 90 percent of American homes have a microwave. AccordinglyNational Fire Safety Association, cause microwaves4 percent of kitchen-related house fires per year(PDF) and 1 percent of associated deaths. A similar percentage of households have a stove or hob, but these appliances are responsible for 62 percent of cook fires and a whopping 89 percent of deaths.

However, it is advisable to remain near the microwave while it is in use so that you can stop small fires before they become large flames. But of all the safety hazards in your kitchen, microwave ovens are far from the top of the list.

For more information see ourGuide to the best microwave ovens.


1.Bob Schiffman is a patent holder in microwave technology and advises companies in the microwave field, but does not represent or be paid by manufacturers directly. The International Microwave Power Institute is a member of the trade group.
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How can I use microwave safely? ›

Food safety tips for microwaves
  1. Use only containers, lids, and wraps that are microwave-safe. Remove food from any packaging that isn't microwave-safe.
  2. Defrost food completely before cooking it in a microwave. ...
  3. Cook food immediately after defrosting.
Oct 1, 2018

Is it safe to use microwave after burning? ›

Is it Safe to Use a Burnt Microwave? If your microwave simply smells and you can remove the burned-on residue, it's safe to resume use once it's clean. But exercise caution—and maybe invest in a new appliance—if any part of the microwave itself appears burned or damaged.

Why is microwave burning? ›

Food-based fires in a microwave almost always happen because someone overestimated or mis-entered the cook time. An extra three minutes can be the difference between a nicely baked potato and a charred, smoky mess.

How do you prevent a microwave from burning? ›

Use oven mitts or potholders when moving hot food from ovens, microwave ovens or stovetops. Never use wet oven mitts or potholders as they can cause scald burns. Replace old or worn oven mitts. Open heated food containers slowly, away from your face.

Is it safe to sit near a microwave? ›

Microwave radiation leaks are hard to detect because you can't smell or see microwaves. The U.S. Food and Drug Administration (FDA), which regulates radiation-emitting products such as microwave ovens, advises against standing directly in front of or up against the oven while it is operating.

Is it safe to sit close to a microwave? ›

Those features greatly limit exposure to levels of radiation that are already low. And since the radiation levels drop sharply with increasing distance, the levels two feet away are about one-hundredth the amount at two inches. Proximity to a microwave oven is not dangerous.

What to do with burnt microwave? ›

Remove any debris or loose burnt pieces from the microwave, then mix 1 cup of water with 1 tablespoon of either lemon juice or vinegar in a microwave-safe container. Heat for 2-5 minutes. Wipe the interior with a sponge or paper towel. Cleaning tip: Don't like the smell of vinegar or lemon juice?

How long should a microwave last? ›

With normal usage for an average family and good maintenance, a microwave often lasts for 7 to 8 years. If the microwave is used less frequently by a single person or a couple and is well-maintained, the lifespan can increase to up to 10 years.

Is it safe to use a microwave after burning plastic? ›

Yes you can, but, remove ALL the melted plastic, just leave it to cool and it should just peel off, give it a quick clean, or better still, a quick steam, use half a cup of water with a little vinegar in, that should get rid of the smell of plastic.

Is it safe to use a microwave that has peeling paint inside? ›

If the coating is actively flaking or paint is peeling anywhere inside the oven cavity (including under the turntable) discontinue the use of the microwave and replace it. The microwave is not repairable.

How do you know when a microwave is unsafe? ›

Smoke, sparks, and burning smells.

These are signs of a serious and urgent problem. Stop what you're doing, and turn off and unplug the microwave immediately. There's no going back if you see smoke or sparks, or smell something burning. Your microwave is failing, and it's time for a replacement.

How far should you stand from a microwave? ›

Standing farther away from the microwave decreases your risk of encountering any microwave radiation. This is because microwave energy decreases as you get farther away from the microwave itself. Try standing a few feet away from the microwave to reduce your risk of exposure when heating up food.

How do I know if my microwave is safe? ›

Call the phone inside the microwave.

All microwaves are FDA approved and emit tiny amounts of radiation. If your phone rings, the seal on the door or the door interlocking mechanism might be broken. In this case, replace your microwave.

What happens if you stand in front of a microwave for too long? ›

In theory, microwaves can heat body tissues in the same way they heat food, and at high levels, microwaves can cause burns and cataracts, according to the FDA.

What happens when a microwave overheats? ›

If the Microwave is overheating and shutting itself down, this is caused by high voltage parts inside the unit getting too hot the leading the thermal cut-out switch to be activated as a safe feature to prevent further overheating.

How long does it take to get burnt smell out of microwave? ›

Deodorize Microwave Overnight

If the burnt smell persists, you should deodorize the microwave overnight using baking soda. If you don't have baking soda, you can use activated charcoal instead. Whichever you choose, put it in an open bowl and leave it in your microwave for 8 hours.

What is the best cleaner for burnt microwave? ›

Add baking soda to a small, microwave-safe bowl, then add water to create the mixture. Microwave the mixture for 5 minutes, then remove the bowl and wipe down the inside of the microwave with a clean rag or paper towel.

What is the fastest way to clean the inside of a microwave? ›

Start by mixing at least two tablespoons of baking soda with one cup of water in a microwave-safe container. Microwave the mixture on high for five minutes. This mix will create extra-dense steam that breaks up grime and kills bad odors. After five minutes, carefully remove the container.

What is the best and easiest way to clean the inside of a microwave? ›

Baking Soda and Water

Baking soda is a natural deodorizer, cleaner, and mildly abrasive, so it's one of the best ways to clean microwave stains and buildup. Mix baking soda and water into a thick cleaning paste and apply it to baked on grime and stubborn stains.

What are the 3 safest materials you can use in a microwave? ›

Paper cups, cartons, cling films and thermo plastics are suitable for microwave cooking. Metal or foil containers should never be used as these reflect the microwaves. Melamine ware also tends to crack when heated.

Is Tupperware microwave safe? ›

According to Tupperware, plastic Tupperware can go in the microwave as long as it has the microwave safe Tupperware symbol. The Tupperware microwave safe symbol looks like 3-5 wavy lines, and you'll find it on the bottom of your food storage containers.

Why not to microwave an egg? ›

Microwaves heat so quickly that steam builds up faster than an egg can 'exhale' it through its pores and the steam bursts through the shell,” the site warns.

What is the most common cause of microwave failure? ›

The most common cause of microwave failure is its magnetron. The magnetron is what produces the microwaves that cook your food, and it's also the part that is most likely to burn out. Symptoms of a faulty or burned-out magnetron include a microwave that doesn't heat food properly or doesn't work.

Are 20 year old microwaves safe? ›

If you take good care of your microwave up into its old age, there's a low risk of harm, but if it's damaged in any way you may want to get it checked out. If you've looked after it well, there's no reason why a vintage microwave should be dangerous.

How much should you pay for a microwave? ›

Small models start around $50, and midsized models are typically in the $100 to $300 range.

Is it better to microwave with plastic lid on or off? ›

If you're going to microwave food in a plastic container, it's best not to use the plastic lid. The concentration of steam that will be produced in a covered container raises the internal temperature of the container even further, which can lead to more leaching of chemicals into your food.

What plastic should not be microwaved? ›

Avoid plastic containers labeled 3, 6 or 7—these are never microwave safe. Single-use plastic is usually a no-go for the microwave, and most takeout containers fall into this category. And if the plastic isn't labeled or the container has visible damage, it's safest to skip the microwave in these cases, too.

How do you clean a microwave after melting plastic? ›

Acetone or nail polish remover: Saturate the plastic residue with acetone-based nail polish remover, and allow it to work for five minutes before scraping. Baking soda: If you prefer a more natural method, mix some baking soda with a few drops of water to make a paste.

What is the inside of a microwave coated with? ›

All microwave cavities are made of metal. The interior is either stainless steel or painted steel with a special microwave paint coating.

Why is the inside top of my microwave peeling? ›

Haier - Microwave Interior Paint Peeling. Peeling paint can be caused by frequently heating items which produce high amounts of steam. If the condensation caused by this steam is not wiped off directly after use it may cause the paint to lift over time resulting in peeling paint.

How long should you let food sit after microwaving? ›

Microwave and food manufacturers often recommend leaving food to stand for a few minutes after cooking or defrosting. This is important for safety as it helps to even out the temperatures and eliminate hot spots. A good rule of thumb is to leave food to stand for roughly half the microwaving time.

Do you need ventilation around a microwave? ›

A well-designed microwave will need 3” of clearance at the top and the sides, with at least 1” at the rear. In other words, if you are asking 'does a microwave need space around it? ' the answer is yes. It ensures the right level of airflow and protects the appliance.

What should you not put on a microwave? ›

Anything made of or containing steel, iron, copper or other hard metals should never go in your microwave. Metal surfaces reflect microwaves, which increases the heat inside the appliance and could lead to a fire.

Which food containers are safe for the microwave? ›

Glass and ceramic containers, along with plastic utensils that are labeled “microwave safe” are good choices. Do not use glass or ceramic that contains a metal rim.

Is it OK to microwave leftovers twice? ›

There are no limits to how many times you can safely reheat leftover home-cooked meals. However, best practice is to limit the number of times you do so. More often than not, you wouldn't need to reheat one type of dish more than once. If you are making meals in bulk, separate and store them in individual portions.

Can you put food back in the fridge after it's been microwaved? ›

After each reheating, leftovers will be safe in the fridge for an additional three to four days. Because the quality decreases each time food is reheated, it is best to reheat only the amount needed. Cooked foods that cannot be used within four days should be frozen for longer, safe storage.

How do you air out a microwave after burning food? ›

Wipe the interior with a soft cloth dipped in water and a little dish soap. On stainless steel models, rub in the direction of the metal's grain. Rinse the microwave with clean water and dry with a soft, lint-free cloth. Leave the microwave open for 2-3 hours to let it air out.

How do I know if my microwave is venting properly? ›

The tissue test below can be used to check for proper draw of the vent: Turn the vent fan on HIGH and hold a tissue or paper towel under the vent area. The suction should hold the tissue or paper towel in place. The draw is equal on both sides.

Where do you vent a microwave? ›

Microwaves are shipped from the factory to vent out the top (vertically) but can also be vented out the rear (horizontally). The duct must be the sizes listed above for proper draw of air. Both smaller and larger vents than recommended decrease venting performance. Microwaves cannot be ducted into a common duct work.

How much space should there be around a microwave? ›

Account for the following: 1 inch of ventilation space between the microwave and the wall behind it. 3 inches of space from the edge of the counter to the open microwave door to avoid tipping. At least 2 feet of space between the microwave and the range.

Can you put a paper towel in the microwave? ›

The short answer is Yes, for the most part, it's safe to microwave paper towels, but you need to be careful doing it. Almost all brands are safe to use in the microwave. But, anything made of paper doesn't have very much moisture, so they can possibly scorch or burn around the edges when overheated in the microwave.

Why should you not put steel plate in microwave? ›

Metal cookware should not be used in a microwave. Metal will not allow microwaves to penetrate and properly cook the food. When convection cooking in a microwave convection oven, metal and foil can be safely used.

Why you should not microwave food in plastic containers? ›

It's a bad idea to heat food in plastic.

According to the World Health Organization (WHO), microwaving food is generally safe. However, microwaving in plastic containers is associated with increased leaching — the transfer or leaking of chemicals into food.

Is it OK to microwave food in plastic containers? ›

Use glass, ceramic and plastic containers and plastic wrap that are labelled as microwave safe. Always follow the instructions on the label when you use microwave-safe containers to heat food. Never heat or store food in plastic containers that were not intended for food.


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