What Should You Never Put in an Air Fryer? 12 Things to Avoid

Air fryers feel like they can do anything — and enthusiastic owners will try anything. But there are things that genuinely don’t belong in that little convection box, ranging from “makes a mess” to “actual fire hazard.” Here’s what you should never put in an air fryer, and the science behind each one.

The definite no’s

1. Battered foods with wet batter

Tempura-style wet batter drips straight through the basket before it sets, creating a burnt-on mess and pale, soggy coating. Air fryers need the batter to be already set (like frozen breaded products) or use a dry coating — flour, egg, breadcrumbs works brilliantly.

2. Loose leafy greens (on their own)

Kale chips are the exception people cite — but unsecured spinach or rocket leaves get blasted around by the fan, hit the heating element, and burn. If you must, weigh them down or use a rack. Mostly, just don’t.

3. Whole roasts with bones sticking out

Anything that touches the heating element will scorch and smoke. If your joint is too big for the drawer with clearance on all sides, it’s too big for the air fryer. Use the oven.

4. Popcorn

Kernels get blown into the element, unpopped kernels rattle around, and most air fryers can’t reach the sustained even heat popcorn needs. You’ll get half-popped kernels and a burnt smell. Get a £15 popcorn maker instead.

5. Cheese on its own

A slice of cheese in an air fryer becomes a molten blob that drips through the basket and welds itself to the bottom. Cheese on things (pizza, toast, breaded mozzarella sticks) is fine — cheese as the thing is a disaster.

6. Large amounts of liquid or soup

Air fryers aren’t designed for liquids. Sauces and soups slosh, spill, and can damage the electronics. A tablespoon of sauce to glaze is fine; a bowl of soup is not.

7. Paper towels or loose paper

The fan will blow them into the heating element. Fire risk, full stop. Parchment liners designed for air fryers (with holes, weighed down by food) are fine — kitchen roll is not.

8. Plastic (obviously, but people do it)

Any plastic container, wrap or utensil that isn’t explicitly heat-safe will melt. This includes the plastic trays some foods come in — always transfer to the basket. Silicone accessories rated for high heat are fine.

The “technically possible but don’t” list

9. Very fatty meats without draining

Duck legs, fatty bacon, lamb chops — the fat renders, pools, and smokes at high heat. It works if you drain the drawer halfway, but unattended it’s a smoke-alarm situation. Pat dry, cook in batches, drain once.

10. Fresh greens like broccoli (without oil)

They’ll dry out and scorch before they cook through. Toss in oil first — it makes all the difference.

11. Toast with butter already on

The fan blows lightweight toast around and the butter smokes. Toast plain bread, butter after. (Or just use the toaster — the right tool for the job.)

12. Anything with a loose, sugary glaze

Honey or sugar glazes burn at air fryer temperatures long before the food cooks. Add glazes in the last 2-3 minutes only.

Materials: what’s safe in the basket?

• Safe: the basket itself, oven-safe metal, cast iron (small), silicone moulds rated to 230°C+, air-fryer parchment liners.
• Not safe: plastic of any kind, paper towels, wax paper (melts), melamine bowls, anything not rated for high heat.
• Aluminium foil: safe if weighed down by food and not blocking airflow — but don’t cover the whole basket, or you defeat the convection.

What air fryers ARE great for

To end on a positive note: roast potatoes (the best you’ll ever make), chicken wings, sausages, roasted veg, reheating pizza and fried food (better than the microwave by miles), frozen snacks, and — my favourite — using it as a second oven at Christmas. If you’re comparing costs, how much a coffee costs on average in London puts kitchen gadget economics in perspective: the air fryer pays for itself; the £4 latte habit doesn’t.

And if you’re buying fresh produce to cook in it, wonky veg boxes are the cheapest way to keep it stocked with quality ingredients.

For manufacturer safety guidance, check your model’s manual — and the Which? air fryer reviews include safety notes from lab testing.

What should you never put in an air fryer? Reader questions answered

Can you put aluminium foil in an air fryer? Yes, with caveats: it must be weighed down by food (loose foil flies into the element), and don’t cover the entire basket — blocking airflow defeats the convection that makes the air fryer work. Use it to wrap delicate items or line the drawer for easy cleaning, not as a full cover.

What about baking parchment? Only parchment liners designed for air fryers — they have holes for airflow and are weighted to stay put. Regular baking paper can blow around; never preheat with parchment and no food on it. Wax paper is an absolute no — the wax coating melts at air fryer temperatures.

Can you cook a steak in an air fryer? Surprisingly, yes — and it’s decent. A thick steak (3cm+) at 200°C for 8-12 minutes, flipped once, gives a good crust and pink middle. It won’t match a cast-iron sear, but it’s far better than most people expect. Pat the steak very dry first and don’t overcrowd.

Can you reheat pizza? This is one of the air fryer’s greatest hits: 3-4 minutes at 180°C gives you a crisp base and melted top — vastly better than the microwave’s soggy sadness. Leftover chips, fried chicken, spring rolls: all revived brilliantly. If you only use your air fryer as a reheater, it’s still worth owning.

Can you bake a cake in an air fryer? Small ones, yes — in a suitable pan that fits with airflow around it. The top browns fast (tent with foil if needed), and the texture is slightly denser than oven-baked. It’s handy for a quick single-serve dessert, not for the Christmas cake. And whatever you bake, remember the golden rule from the main guide: if it can drip, fly, or melt onto the element, it doesn’t belong in there.

The takeaway

Never put wet batter, loose paper, plastic, loose leaves, or large volumes of liquid in your air fryer. Respect the heating element clearance, weigh things down, and drain fatty cooks halfway. Follow those rules and the air fryer remains the hardest-working, safest appliance in your kitchen.