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Microwave Oven

How to Tell If Plastic is Microwave Safe? – Quick Guide


We often reheat our food in their containers without bothering to check if they are microwave safe or not.

Knowing if a plastic container is safe to be put in microwave is important. Plastic containers, plates, or utensils aren’t all made equally. Some are resistant to microwave heat and others aren’t.

Microwaving a non compatible plastic container is dangerous not just for the immediate environment but also for your health.

This article will discuss how to tell if plastic is microwave safe. We will discuss how unsafe plastic can harm your food or even your container.

We will also discuss how to know if a particular kitchenware is microwave-safe or not.

Lets first look at how microwave ovens work briefly. This information may come in handy as you read about safe containers.

How Does Microwave Works?

A microwave oven uses high-frequency electromagnetic radiation to heat food.

These electromagnetic heat waves stir the molecules of food or beverages and make them vibrate rapidly. This vibration of food molecules produces heat.

Microwave safe plastics are not affected by this radiation at the temperature that microwave oven operates at.

Also Read in Detail: How does a microwave oven work?

Popular Microwave Safe Plastic Containers

How To Tell If Plastic is Microwave Safe?

There are many ways to check if a plastic container is microwave safe.

1. Look for FDA Approved Symbol

How to Tell If Plastic is Microwave Safe

Microwave safe symbol. Source: NUSPINKIDS.com

An easy way to determine if a certain plastic container is safe for the microwave is to look for the special “microwave safe ” symbol.

The symbol with microwave and wavy lines indicates that particular cookware is safe to be put inside the microwave. You can look for the symbol on the bottom of a container.

Microwave-safe containers are gone through rigorous testing and approved by the FDA to designate a particular container is safe to be used in a microwave.

So a microwave-safe stamp can ensure the consumers that a particular plastic container can withstand the microwave heat waves.

2. Use the Recycling Code as a Guide

The number that show see between a triangle embossed on a plastic container is its recycling number.

These recycling numbers can tell you a lot about whether they are suitable for microwave oven or not.

plastic recycling number

Plastic Recycling Numbers. Source: Eartheasy

  1. PETE – Only intended for One-Time use and therefore not safe for microwave UNLESS otherwise specified by the manufacturer
  2. HDPE – Sometimes safe for microwave especially if approved. Most caution against microwaving it.
  3. PVC – Unsafe but you don’t find food containers made out of PVC anyways. Contains Bisphenol A (BPA) which is a dangerous checmical.
  4. LDPE – Mixed commentry about whether it is safe or not for microwave.
  5. PPBest Choice for Microwave. PP are generally labeled as microwave safe.
  6. PS – Not suitable for microwave at all
  7. Others – Do not use in microwave

Best Polypropylene Containers

3. What about an Unlabelled Container?

Those containers that do not contain any label indicating if it is safe or unsafe for microwave does not necessarily mean that they are unsafe to be put in a microwave.

It simply means that they have not gone through the testing that would determine if they are safe or not.

As no testing approve these plastic containers, it is better to avoid such kitchenwares.

How Can we Know if an Unlabelled Container is Microwave-safe?

As we mentioned above, microwave waves work by stirring the molecules of food. The microwave-safe containers do not absorb the heat waves but allow them to pass through to the food inside.

An easy way to determine if a container is microwave-safe is to place it in a microwave with water in it for half a minute. If the container gets hot, it is not safe to be used in a microwave.

A container should not absorb heat but pass through the heat to the food inside it.

When trying out an unlabelled plastic in a microwave, make sure that you will not be heating anything edible or potable in it.

Also Read: Where can I recycle my Microwave?

Commonly Found Plastics and If they are Safe for Microwave

Most commonly found plastic are :

Polypropylene – Recycle Code 5


A Typical Polypropylene Container

It’s a thermoplastic polymer. It has a high density and can resist heat.

A common type of polypropylene is baby bottles and plastic cups.

These containers are best to be used in the microwave if you want to use plastic anyway.

High Density Polyethylene – Recycle Code 2

High-density polyethylene is hard and can withstand high temperature. It is commonly used in making toys and milk jugs etc.

It is not perfectly safe, but you can put it in the microwave if approved by the manufacturer.

Polyethylene Terephthalate – Recycle Code 1

Most common plastic of polyester family. It is used in clothing, food containers and plastic bottles.

It can withstand heat, but it is intended for one time use and thus should not be used in the microwave unless it has some reinforced or strengthening material that prevents the plastic from getting into food.

Why are Plastic Containers not Safe?

We all know plastic inside our food is a health hazard.

It contains certain toxic chemicals that may affect your food as well. These chemicals leach out in food more readily when the container is heated.

That makes the common practice of reheating your leftover food in the microwave very dangerous.  But not all plastic containers are unsafe in the microwave. Some types of plastic are approved by the FDA to be put in a microwave.

So here is how unsafe plastic can be harmful:

Contaminate Your Food

The worst hazard an unsafe plastic container can produce is contaminate your food.

If heated beyond limits, certain toxins can contaminate your food, making it cause many health hazards.

Phthalates and bisphenol-A (BPA) can cause many developmental and reproductive issues in both children and adults.

Disfigure Your Container

If a container is not microwave safe, that means, in simple words, that It cannot withstand the heat.

Heating it beyond its limit can cause the plastic to melt or disfigure. This is also a fire hazard.

Also Read: How much radiation does a microwave oven emit?

Some Tips for Using Microwave Safely

These are some tips that can help you use a microwave safely.

  • Use only plastic containers with a microwave-safe symbol.
  • Even containers with a microwave-safe symbol should not be used unless you know they are made of BPA free plastic material.
  • Never use any container that does not have a symbol on it even if it seems a very strong plastic.
  • Use the microwave-safe glassware and ceramic containers instead of plastic. You should avoid using plastic as much as you can in your day to day kitchen routine.
  • Don’t reheat take-outs leftovers in the same restaurant provided container.
  • Don’t wrap your food with plastic cover if you are reheating or cooking in the microwave.
  • Don’t use paper or brown bags in the microwave. These bags have a coating of glue that melts with heat and may enter in your food as you heat them.


Here we learned about a few simple ways on how to tell if plastic is microwave safe.

Using unsafe plastic in the microwave can cause serious health implications.

However, actively looking for “microwave safe” symbol or looking for “recycle symbol” can help you gauge about the safety of your plastic containers.


1. What is the symbol for microwave safe plastic?

Microwave-safe containers have squiggly lines. This sign can take on a variety of forms, perhaps depicting a microwave or a dish put beneath radiation waves, but the squiggly lines remain consistent. Squiggly lines indicate that you can easily reheat that sucker.

2. How would you determine if a container is safe to use in a microwave oven?

A simple test to verify if a container is microwave safe is to set it in a microwave for half a minute with water inside. If the container becomes too hot to handle, it should not be microwaved. A container should not absorb heat but rather conduct it to the food contained within.

3. What plastic can be microwaved?


4. Is it safe to microwave in plastic?

Microwaving food is usually considered safe by the World Health Organization (WHO). Microwaving in plastic containers, on the other hand, has been linked to an increase in leaching – the transfer or leakage of chemicals into food.

5. What materials should not be microwaved?

Aluminum Foil: When microwaved, crinkled foil might cause a spark. Cookware made of metal: Metal can cause the dish to overheat and become damaged. Single-use yogurt containers are prone to melting and leaking phthalates. Containers that have been torched generate cancer-causing substances.

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