Can Styrofoam Go In The Microwave? (Explained)

Microwave ovens have become a part of many homes. And as such, most people have learned to keep metals, aluminum foil, and other microwave unsafe utensils out of the appliance.

Such containers can cause fire and ruin your microwave, which you’d rather not experience, right?

You also don’t want to risk the health of your loved ones by using utensils that can leach chemicals to your food when placed in the microwave.

So, can Styrofoam go in a microwave? Styrofoam is not designed for use in the microwave. Avoid using it in the appliance as much as possible.

What is Styrofoam?

Can Styrofoam Go in a Microwave

Styrofoam is a type of polystyrene foam generally used in the building industry. Over the years, it has been used in making disposable cups, plates, and takeout containers.

Styrofoam is popular because of its lightweight, durability, insulating, and affordable features.

And although it doesn’t break down for years, Styrofoam melts when exposed to high temperatures to form carbon and water as by-products.

Is it Safe to Microwave Styrofoam?

Most Styrofoam melts when exposed to heat (even at low temperatures); hence not the best to use in the microwave. They, however, work excellently in the fridge and are also great for carrying food to work or school.

Although using microwave-safe Styrofoam utensils is acceptable, you still have to be careful enough. Don’t exceed the stated heating temperature.

You also need to minimize the power setting to low temperature even when using microwave-safe Styrofoam utensils.

Note that Styrofoam containers are typically made for reheating and defrosting temperatures and not cooking in high temperatures.

Microwave-Safe Styrofoam

Microwave safe Styrofoam is tested to meet the safety standards for microwave use. However, it’s not commonly available in the market.

Microwave-safe containers are made from safe materials, have fewer toxic compounds and a higher melting point. Due to their enhanced stability, these products don’t melt quickly when heated.

Check for the safety label imprint to determine whether your utensil is microwave-safe. Also, should you discover visible damage to the container after heating it in a microwave, dispose it and the food in it.

You should also not heat Styrofoam food containers with cracks or use them to store your food. Such containers release toxins into the food and can thus harm your body.

Traditional Styrofoam

Although it’s the most common type of Styrofoam, traditional Styrofoam isn’t microwave-safe. It appears typically stable when you use it under average temperatures but starts to melt when you heat it at high temperatures.

And even if there’s no visible damage, the microwave can make styrene (a toxic chemical) leach into your food.

Styrene is a carcinogen linked to cancer and is also dangerous to the reproductive system.

How to Tell Whether a Styrofoam Container is Microwave Safe

If you want to reheat food but can’t tell whether the Styrofoam container you intend to use is safe or not, consider the following:

  • Look for a microwave-safe symbol

The microwave symbol is wavy lines on the container. If the container has the #5 indication, it was made using polypropylene and thus perfect for microwave use.

  • Check for the CPET or #1

If the dish has the CPET or #1 symbol, it’s safe to microwave. Containers with these symbols are used in ovens and can withstand high temperatures.

  • Styrofoam #6 is not fully microwave-safe

Number 6 Styrofoam containers are for disposable use only. Don’t use them in the microwave.

  • APET is unsafe to use in the microwave

APET Styrofoam includes plastic containers and water bottles. Typically, most products used to store cold food aren’t safe for reheating.

  • Styrofoam #7 is unsafe to use in the microwave

Styrofoam #7 containers are made of insulation properties and help keep your food warm traveling. It would be best if you never used them for heating food in the microwave.

  • Containers made of harvest fibers are not microwave-safe

Containers such as paper cups, plates, or takeout containers are not suitable for the microwave as they are coated, glued, or sealed with additives that could leak into your food.

Things to Know Before Using Styrofoam in a Microwave

After getting a microwave-safe Styrofoam container, you still need to pay extra attention to avoid disappointments.

Consider the following tips:

  • Avoid reheating your food more than once.
  • Ensure that your Styrofoam container has a microwave-safe icon symbol at the bottom.
  • Check the condition of your microwave to ensure that it’s in good condition before putting it in your Styrofoam container.
  • Cover your food with a paper towel or microwave-safe container to avoid splattering the food in the microwave.

Frequently Asked Questions

Q: Can Styrofoam cups go in the microwave?

Styrofoam cups can only go in the microwave if they come with a microwave-safe label. And even if microwave-safe, you can’t reheat them in high temperatures or leave them in the microwave for long.

Q: Is Styrofoam toxic?

Styrofoam contains styrene, which is toxic and hazardous.

Q: Why are Styrofoam containers bad for you?

Styrofoam containers leach benzene and styrene to your food. The two chemicals are highly toxic.

Q: Is Styrofoam plastic?

Styrofoam is a thermoplastic polystyrene foam product.

Q: Can Styrofoam 6 go in the microwave?

Styrofoam 6 is not safe to use in the microwave.

Q: Does Styrofoam melt in the microwave?

Styrofoam melts in the microwave if heated or reheated in high temperatures.

Q: Can you put Styrofoam to-go boxes in the microwave?

You can put Styrofoam to-go boxes in the microwave if they are microwave-safe.

Q: How long can you microwave Styrofoam?

You can microwave Styrofoam for only 30 seconds.


With Styrofoam, you have to be extra careful if you intend to use it in the microwave. Although labeled microwave-safe, you still have to regulate the temperature since you can’t use it in high temperatures.

And did we mention that you can’t microwave a Styrofoam container for long, even if it’s microwave-safe (1)?

Follow the manufacturer’s guidelines(2) since you don’t want to consume food rich in styrene. With Styrofoam containers, there’s no room for guesswork. A slight mishap and you compromise your health.