- Keep metal, Styrofoam, brown paper and single-use plastics out of the microwave.
- Always use microwave-safe containers and check manufacturer labels.
- Vent lids or loosen tight lids to prevent explosions and allow steam to escape.
Since the 1970s, the microwave has been a kitchen game-changer, using short radio waves to quickly heat food, and making everyday tasks like steaming veggies or reheating leftovers effortless.
Given how often most people rely on microwaves, using them safely matters. Putting the wrong item inside can create serious health or fire hazards. Here’s what food safety experts say about common kitchen items you always should keep out of your microwave.
1. Metal Containers or Utensils
Never put anything metal in the microwave, cautions Zachary Cartwright, Ph.D., a food scientist. “Metal—foil, utensils, travel mugs—causes arcing and fire risk.”
Arcing occurs when metal reacts with the electricity produced by the microwave, which can create sparks. These sparks generate intense heat that can damage the appliance or even start a fire.
Arcing can happen if you accidentally microwave a metal utensil or reheat food on a plate with metallic trim. To reduce risk, transfer foods to microwave-safe plates, bowls or containers made of materials like glass or ceramic before heating. “When in doubt, follow manufacturer guidance on containers and cookware,” says Cartwright.
2. Single-Use Plastics
Some plastics are safe for the microwave, which should be clearly labeled by the manufacturer. However, single-use plastics—such as yogurt tubs, sandwich bags and takeout containers—should never go in the microwave. These materials can warp or melt and may release harmful chemicals into your food.
“These plastics are not heat-stabilized,” says Ed McCormick, a food science consultant. “In high temperatures, phthalates can leach out into fatty materials.”
Plastic films and wraps are a bit different. They’re commonly used by frozen-meal companies and are safe to use in the microwave as long as they don’t touch the food and are vented to release steam. To do this, leave space between the wrap and the food and poke a few holes in the film before heating.
3. Paper Bags
Certain types of paper, such as parchment paper, wax paper and even white paper towels, are microwave-safe. Others, however, are not. Brown paper bags and newspaper should never be heated in the microwave.
McCormick notes that impurities or recycled materials in these papers can emit harmful fumes or even ignite at high temperatures.
If you’re reheating takeout, discard this type of paper and transfer food to a microwave-safe container instead. To prevent splatters, cover foods with wax paper, parchment paper, a microwave lid or a microwave-safe ceramic plate while reheating.
4. Styrofoam
If your restaurant leftovers come home with you in plastic foam containers (aka Styrofoam), be sure to remove the food before reheating it in the microwave. “Styrofoam can melt and release harmful compounds,” Cartwright says. “Instead, use microwave-safe glass or ceramic containers and transfer food out of questionable packaging.” Same with plastic foam beverage cups: pour that cold coffee into a microwave-safe mug before reheating it.
5. Sealed Containers
Even microwave-safe containers can be hazardous if they’re tightly sealed. Cartwright explains that jars or other sealed containers can explode as pressure builds up while heating. To stay safe, cover foods loosely and vent lids to release steam and reduce pressure.
Our Expert Take
The microwave is a go-to appliance for any home cook who values speed and convenience—as long as it’s used safely. Keep metal, Styrofoam, brown paper and single-use plastics out of the microwave, and always check that storage containers and disposable products are labeled microwave-safe.
To prevent explosions, never heat sealed containers. Instead, cover food loosely with wax or parchment paper, a ceramic plate or plastic wrap vented with a few small holes to let steam escape. These simple precautions help keep both your food and microwave safe.
