Can You Put Styrofoam In A Microwave: Reheat Food Safely

Microwaves help up save time when cooking, defrosting, or even warming food. Sometimes, people find it convenient to reheat take-out food packed in Styrofoam. But, how safe is it?

Styrofoam may not qualify as a microwave-safe material for use in a microwave. However, the containers are best for keeping your food warm by insulating it. They are best used for traveling.

Can you put Styrofoam in the microwave? Styrofoam is not a safe material to use in a microwave. It is a synthetic material containing a combination of toxic chemical compounds. The chemicals leach into your food reaches high heat in a microwave.

There are two main types of Styrofoam containers in the market. One is microwave safe; the other is not. The regular Styrofoam is not microwave safe, while the other is hard to find.

To understand why Styrofoam may not be microwave safe, let us look at what Styrofoam is made of.

What Is Styrofoam Made Of?

Styrofoam is made from polystyrene, which is a petroleum-based product containing styrene monomers. The name Styrofoam is only a trademark owned by The Dow Chemical Company.

Styrene is converted into polystyrene during a chemical process known as polymerization. Hydrofluorocarbon is then added. The mixture is left to expand under pressure forming a product.

The high pressure gives Styrene its insulating properties as it contains 95% air. The high amount of air helps the Styrofoam stay afloat.

Styrofoam may melt even when heated under normal temperatures. It emits toxic carbon monoxide gas and carbon black.

Learn more about what makes Styrofoam is so dangerous and the greater issues it can potentially bring by checking out the video below!

Traditional Styrofoam Vs. Microwave-Safe Styrofoam

  • Traditional Styrofoam

Traditional Styrofoam is the most common Styrofoam used to package take-out food. It is unsafe for use in a microwave.

Microwaves increase the risk of styrene and acetone chemicals leaching into your food. These chemicals have a cancerous effect.

  • Microwave-safe Styrofoam

The microwave-safe Styrofoam is hard to find, but it meets the safety requirement. However, it still contains toxic compounds and melts under high temperatures.

The difference between traditional Styrofoam and microwave-safe Styrofoam is their toxic levels. The latter has less toxic compounds.

Common Types Of Styrofoam Containers

  • Coffee cups
  • Cup noodles
  • Styrofoam plates
  • Take-out containers

Warning! Do not consume the food when you notice a crack in the Styrofoam container after microwaving it. Throw away the food and the container. Never reuse a damaged Styrofoam container.

Heating Up Styrofoam: What You Need To Know

Styrofoam melts even at low temperatures. Food-use Styrofoam containers made from expanded polystyrene are unsafe for use in an oven.

The ‘food-safe’ Styrofoam containers melt at about 160 degrees Celsius. You may begin to notice changes in format about 100-120 degrees Celsius. The containers begin to deform.

According to, The National Institute Of Standards and Technology (NIST), polystyrene starts decomposing at 200 degrees Celsius. It breaks down at around 224 degrees Celsius.

Does Heating/Microwaving Styrofoam Cause Cancer?

Heated Styrofoam leaches toxic Styrene and acetone into your food. According to a 2011 study, styrene exposure increased the risk of different cancers in rats and mice.

The study indicates that Styrene workers had increased mortality rates. They were at risk of pancreatic and esophageal tumors.

There were also increased Lymphohematopoietic cancers cases among the workers.

Can You Put Styrofoam In The Microwave On Defrost?

Defrosting food in a microwave helps to hasten meal preparation. You need to follow important food safety factors. Among the safety measures include avoiding the use of Styrofoam.

According to USDA, avoid defrosting food using foam or plastic warps. These materials are not heat-stable when exposed to high temperatures.

Take off the Styrofoam packaging and plastic warp from your food when you remove it from the freezer. The foam may melt in the microwave, causing the leaching of toxic chemicals to your food.

Use a microwave-safe container such as glass or ceramic and set the defrost function at 30% power.

Defrosting takes about 7 minutes which is long enough to melt Styrofoam if used in the microwave.

Meat is very sensitive to defrosting. Meat may partially cook when defrosted. This means that it is more likely to absorb the toxic chemicals from Styrofoam.

If left to sit after defrosting, meat accumulates bacteria leading to food poisoning. Cook it immediately after defrosting. Ideally you would have a plate or surface that allows for the meat to quickly thaw. A great choice for that surface you are looking for can be found from Amazon by the Defrost Magic line of defrosting trays. Check out more information here!

How To Safely Defrost Food In A Microwave Using A Styrofoam-Free Container

  • Check the packaging for instructions on defrosting.
  • Remove the food from the packaging, especially if it’s plastic or Styrofoam.
  • Put the food in a microwave-safe container. Check for a microwave-safe label if you are not sure about the safety of the container.
  • Open the lid slightly if using a covered container to allow space for steam to escape.
  • Set your microwave on defrost at about 30% heating power for foods that take long to defrost. Use 50% power may for soft foods such as vegetables.
  • Keep checking for defrosting. It may involve consistent stirring to allow heat to distribute evenly in the food.
  • Remove part of your food from the container as it defrosts. Remove the microwave-safe container from the microwave when the remaining food defrosts.

How To Tell If Styrofoam Is Microwave Safe

There are different ways to tell if a Styrofoam container is microwave-safe or not.

Look For Microwave-Safe Label Or Logo At The Bottom Of The Styrofoam Container

Ensure there is a ‘microwave-safe’ label at the bottom of your Styrofoam container. Sometimes, it comes as a logo with wavy lines that resemble a microwave.

Different manufacturers may choose to use different symbols. Identify these symbols and labels before using the Styrofoam container in your microwave.

It is a lot easier to find microwave safe Styrofoam nowadays, and a number of restaurants have changed over from the traditional Styrofoam of the past. The company HeloGreen is one of those main providers that have taken the market by storm. Check out their listing on Amazon, right here!

Look At The Recycling Number/Code To Tell If The Styrofoam Container Is Safe

Polystyrene manufacturers use numbers to represent different types of polystyrenes. The numbers tell whether the polystyrene is safe for microwave use or not.

The numbers are enclosed in a triangular recycling symbol at the bottom of the container. Arrows form the three sides of a triangle. Plastics have this symbol as a regulatory requirement.

PVCs Recycling Code Numbers And Their Meaning

  • #5- Microwave safe

The polystyrene material used to make the Styrofoam is safe for use in a microwave.

  • #1 #2 #4- Partially safe

PVCs with numbers 1,2,4 could be safe. They store margarine, yogurts, or cream.

Some may withstand heat based on their chemical reinforcement. This means that it is safe for use in a microwave. Only use these PVCs for s short period and low temperatures.

 PVCs with numbers 1, 2, 4 melt under high temperatures or when heated for long. This leads to the leaching of toxic chemicals into your food. It may also cause damage to your microwave.

  • #3 #6 #7- Unsafe

PVCs with numbers 3, 6, 7 have high carcinogenic risk factors and contain Bisphenol-A.

BPA is a lethal chemical compound found in plastics. Avoid using such containers to heat your food in a microwave.

There has been a debate on whether to use PVCs #6 labeled ‘microwave-safe. Here are few guidelines on how to use the #6 Styrofoam.

Tips Of Using Microwave-Safe #6 Styrofoam In A Microwave

  • Ensure that the microwave-safe label or logo is present.
  • Check for damage or cracks on the container. Do not use Styrofoam in the microwave if you notice damages or cracks.
  • Switch off the microwave, and throw away the Styrofoam and the food when it starts melting.

Look For CPET/APET Labels On The Styrofoam To Tell If It’s Microwave-Safe

  • CPET is safe for microwave use and also safe for use in an oven. CPET Styrofoam can withstand high temperatures.
  • APET Styrofoam is unsafe for microwave use. Avoid using them to reheat food in microwaves, but they are good for recycling.

If you are not sure about the safety of your Styrofoam container before reheating food, do not use it. Instead, use a glass or ceramic container. These materials are microwave safe.

The FDA places regulations on the types of Styrofoam that come into contact with food.

Manufacturers should use the FDA standards and regulations tests guidelines. They check whether the polystyrene containers are microwave safe.

Manufacturers should send the test result to the FDA for approval. FDA reviews the test data. It then approves polystyrene containers that meet the requirements for microwave use.

How Long Can You Microwave Styrofoam?

Avoid using Styrofoam in a microwave for more than 30 seconds. Styrofoam could start releasing toxins into your food if it stays for long in a microwave.

If the Styrofoam does not have a microwave-safe symbol, do not put it in a microwave oven for a second.

Only use microwave-safe Styrofoam containers at medium power level. Exposure to high heat for long may melt microwave-safe Styrofoam containers.

There are a few things to observe even when heating food in a microwave-safe container. They include;

Tips For Microwaving Styrofoam For Less Than 30 Seconds

  • Look for the microwave-safe label/logo
  • Only let the Styrofoam heat at medium heat for a maximum of 30 seconds
  • Remove the Styrofoam from the microwave when you notice signs of melting
  • Leave a small space on the lead to allow room for ventilation during defrosting

Will Styrofoam Catch Fire In The Microwave?

Styrofoam may catch fire when exposed to an open flame. But, it can withstand some degree of heat in a microwave.

It is unsafe to place Styrofoam near kitchen appliances that are a heat source. It increases the risk of catching fire which may damage your house.

Kitchen Appliances To Keep Away From Styrofoam

  • Microwaves
  • Grill
  • Oven
  • Stove
  • Water heaters

Keep Styrofoam ways from any electrical wiring that poses a risk of ignition.

Is Styrofoam Flammable?

Polystyrene in its purest form is flammable when heated even at low temperatures. It emits hazardous gases into the environment, increasing the risk of global warming.

Regular food-safe Styrofoam containers are thin hence not suitable for heating or cooking. They pose a fire hazard that may damage your appliance and the entire household. 

At What Temperature Will Styrofoam Catch Fire

Styrofoam catches fires when exposed to open flames of about 360 degrees Celsius. At 427 degrees Celsius, Styrofoam will auto-ignite and may cause grave damage.

It emits carbon monoxide and Carbon black, which are hazardous to the environment. You will notice black soot, which is a sign of unbroken compounds.

Below Is a Data Table Analyzing Common Items You Should Not Use in a Microwave:

What not to use in the microwave Percentage of total results
You definitely do not want to put non-microwaveable Plastics/Containers in a microwave.27.27%
Unless explicitly stated, it is very dangerous to put any sort of Metallic materials (such as aluminum) in a microwave.22.73%
Avoid putting Hot Peppers in a microwave, otherwise you can create vapors that will irritate your lungs. 18.18%
It is highly-recommended that you do not use plastics such as Styrofoam in a microwave.12.50%
A probably won’t come as a surprise, but Light-bulbs are not micro-wave friendly, and explosions can happen as a result.12.50%
Dry Materials such as paper and fabric do not belong in a microwave and can result in fires9.09%
Although it’s a fun experiment to observe, microwaving a CD will result in releasing toxic vapors and destroying the disk.4.55%
Data derived from informative cooking forums online

Is It Safe To Reheat Food In Styrofoam

Polystyrene produces carcinogenic compounds such as Styrene, acetone when heated. The toxic chemicals leach into food, causing negative health effects.

Getting your leftover junk packaged in a Styrofoam container and throwing it in the microwave is convenient. However, instead of filling your stomach, you are filling your body with carcinogens.

As mentioned, chemical compounds in Styrofoam may lead to cancer when leached in food. Other health issues associated with ingesting the chemical toxins include;

Health Risks Of Ingesting Heated Styrofoam/Polystyrene

  • Headaches
  • Stomach irritation
  • Eye irritation
  • Fatigue
  • Reproductive health problems
  • Clinical depression
  • Hearing loss
  • Central nervous system disorders

Styrofoam poses the above health risks even when ingested through the air. A study mentioned earlier showed that styrene workers had a high prevalence of cancers and tumors.

No matter the hunger or hurry you may have to get your meal fixed, avoid using Styrofoam. Here is a reader’s secret to reheating food packed in a Styrofoam container.

Secret To Reheating Styrofoam-Packed Food In A Microwave

  • Always keep a clean microwave-safe container in or on the microwave. It saves you the time and energy of opening shelves and drawers looking for an empty container.
  • A standby microwave-safe container minimizes the temptation to put Styrofoam in the microwave.

Final Thoughts

Styrofoam containers are great for keeping your food and drink warm while on transit. However, avoid using the containers to warm food or drinks in a microwave or oven.

The fact of the matter is that Styrofoam can melt and is known for leaching toxic chemicals into your food when placed in a microwave. While it might be ubiquitous in the usage of restaurant industry, try to keep your personal usage as low as possible.

Related Topics

can you put paper plates in the microwave

can you put aluminum foil in the microwave

Aron Blake

I am the lead copywriter on Homezesty and the Webmaster. I have a lot of experience in home renovations and the creation of style. I enjoy writing and sharing my tips on how to create the best living environment. My Linkedin Profile, My Twitter Account

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