Most of the things you should never put in an air fryer are not exotic. They are everyday habits: using the wrong spray, overfilling the basket, blocking airflow with liners or trusting a frozen product to cook through because it looks done. Below are the items and habits that government and university sources actually warn about, followed by a shorter list of foods that tend to cook badly, so you can tell a real safety problem from a matter of taste.
Eight things never to do in an air fryer
1Air frying frozen raw breaded stuffed chicken
Verdict: use the oven directions on the box, and check that the label does not say raw. In a 2021 Salmonella outbreak notice, the CDC said raw frozen breaded stuffed chicken products can look cooked because they are breaded or browned. It advised cooking them in an oven to 165°F, checked with a food thermometer, and said a microwave or air fryer will not always cook the product thoroughly. The USDA Food Safety and Inspection Service reported that some people who got sick had microwaved the product, used an air fryer or baked it for less than the recommended time without a thermometer.
This warning is specific to raw stuffed products. For other frozen chicken, check whether the package says raw or fully cooked and follow its directions. Fully cooked nuggets and tenders have their own air fryer instructions.
2Nonstick spray with additives
Verdict: avoid it unless your manual allows it. Mississippi State University Extension says store-bought nonstick sprays often have additives that can damage the air fryer basket, and recommends a light spritz to one tablespoon of oil on the food instead. The Ninja Prestige Smart XL owner’s guide separately says not to spray any type of aerosol spray or flavoring inside that oven while cooking, and to grease accessories with cooking oil instead.
Our practical tip: toss food with a little oil in a bowl, or use a refillable oil sprayer if your manual permits it.
3Paper, cardboard, plastic or roasting bags
Verdict: parchment only, and only where your manual allows it. The Ninja Prestige Smart XL owner’s guide says that, with the exception of parchment paper, paper and similar materials must not go in the oven, and lists cardboard, plastic and roasting bags among them. It also urges extreme caution with containers made of anything other than metal or glass. That guide covers one oven-style Ninja model, and other models differ.
Our practical tip: use only liners made for your appliance, put food on them before the machine heats, and trim them so nothing hangs over the edge or sits near the element.
4Foil over the crumb tray, vents or tray holes
Verdict: foil can be fine on an accessory and dangerous in the wrong place. The Ninja Prestige Smart XL owner’s guide says not to cover the crumb tray or any part of the oven with aluminum foil, because that can cause overheating or fire, and not to cover the roast tray holes with foil or parchment. The same guide does allow lining accessories such as the sheet pan, so the rule depends on placement. Mississippi State University Extension does not address foil. Follow the placement rules for your exact model.
5A packed basket or oversized food
Verdict: cook in batches, and keep food off the heating element. Nebraska Extension cautions that an overfilled basket or tray means foods will not cook evenly or reach the proper temperature, and that overfilling also interferes with browning. Mississippi State University Extension also says not to overfill the basket. The Ninja Prestige Smart XL owner’s guide says to prevent food contact with the heating elements, warns that excessive food loads may cause injury or property damage, and says oversize foods must not be inserted because they may create a fire or risk of electric shock.
6Olive oil, butter or margarine at high heat
Verdict: choose a higher smoke point oil, and use only a little. The Ninja Prestige Smart XL owner’s guide recommends canola, refined coconut, avocado, vegetable or grapeseed oil instead of olive oil and lists olive oil, butter and margarine as not recommended. Mississippi State University Extension says less is more, with a light spritz to one tablespoon of oil, and explains that every oil has a smoking point at which it burns. Its table lists avocado oil at 520°F and refined canola at 400°F.
7The base unit in water
Verdict: never submerge it. The Ninja Prestige Smart XL owner’s guide says not to immerse the cord, plugs or main unit housing in water or other liquid, to protect against electric shock. The Ninja Foodi Grill owner’s guide and the Ninja Foodi Smart Grill owner’s guide say the same. Wash the removable basket, tray and pan, then wipe the rest with a damp cloth, as Mississippi State University Extension describes. Do not pour liquids into the basket either, where they can splatter or leak.
8Metal utensils and rough scrubbers
Verdict: use soft tools, in the machine and at the sink. The Ninja Prestige Smart XL owner’s guide says metal utensils must not be inserted in the oven because they may create a fire or risk of electric shock. Mississippi State University Extension says never to use metal utensils to remove crumbs or baked-on grease, and to let the basket cool before washing. The Ninja Foodi Smart Grill owner’s guide says not to clean with metal scouring pads. Soak baked-on grease in hot soapy water instead.
One habit that matters: use a thermometer
Nebraska Extension says a food thermometer is the only way to ensure the safety of meat, poultry and egg products when air frying, so do not judge doneness by color or timer alone. Insert it in the thickest part, away from bone, fat and gristle. It lists the USDA minimums: 165°F for all poultry, including ground poultry, and for casseroles; 160°F for ground beef, pork, veal and lamb and for eggs; and 145°F for fish and shellfish and for steaks, chops and roasts of beef, pork, veal and lamb (with a 3-minute rest for those meats).
Two rules about the machine itself
Give it room. Mississippi State University Extension says to leave 5 inches behind the air fryer for airflow. Ninja’s guides vary by model: the Ninja Foodi Grill owner’s guide says to provide at least 6 inches above and on all sides, while the Ninja Prestige Smart XL owner’s guide says at least 1 inch above and on all sides and to keep it away from curtains, walls and other flammable materials while it runs. Look up your own model, and do not run it under a cabinet or against a wall unless the manual allows it.
Stop using a recalled unit. The U.S. Consumer Product Safety Commission recalled about 2 million COSORI air fryers in February 2023 because a wire connection could overheat, posing fire and burn hazards. The firm had received 205 reports of units catching fire, burning, melting, overheating or smoking. Check the model number on the bottom label against the CPSC recall list if you own a COSORI, and look up your brand if you are not sure.
Foods that need a different method in an air fryer
Foods that need a different method or extra precautions. These are general cooking considerations, not universal bans, and some involve smoke or loose ingredients. The notes are ours, not findings from the sources above. Results and permitted methods depend on your appliance.
| Food | Why it struggles | Better move |
|---|---|---|
| Wet batter (tempura, beer batter) | Thin, wet batter can drip off instead of forming a crisp coating. Ninja’s Foodi Grill guide also notes that loose breading may be blown off by the fan. | Use a flour, egg and breadcrumb coating and press the crumbs on, or a fully cooked frozen breaded product with air fryer directions. |
| Loose leafy greens | Very light leaves can blow around the basket and scorch. | Use a recipe written for air frying, wilt greens in a skillet, or toss sturdier greens in oil. |
| Popcorn kernels | This is our editorial recommendation, not a documented manufacturer ban. Loose kernels can scatter in the basket, and the Ninja guides we checked do not mention popcorn. | Use a microwave or stovetop, or a method your manual approves. |
| Dry rice, pasta and grains | Poured dry into a perforated basket, they have no liquid to cook in and can fall through or scatter. | Cook them first, then crisp them if you like. An oven-safe dish and a method your manual approves is a different matter. |
| Soups, broths and saucy stews | Do not pour liquids directly into an air fryer basket, where they can splatter or leak. | Simmer on the stove or in a slow cooker, or reheat in an oven-safe container only if your manual allows it. |
| Loose shredded cheese | It can melt through the basket holes or lift in the airflow. | Keep cheese contained in a sandwich or suitable dish. Mississippi State University Extension suggests toothpicks or a trivet to hold a grilled cheese sandwich together. |
| Very fatty foods | Rendered fat can cause smoking. | Follow your model’s instructions for catching grease, such as the roast tray in the Ninja Prestige Smart XL owner’s guide. Mississippi State University Extension says white smoke can mean too much fat and suggests water or bread in the drawer for basket-style air fryers. Do not apply that tip to other designs unless the manufacturer permits it. |
| Small chopped vegetables | Pieces can fall through the basket and burn underneath, per Mississippi State University Extension. | Cut larger, or use a perforated tray or liner sized to the basket. |
If grease catches fire: never use water on burning grease or on an electrical appliance. The Ninja Prestige Smart XL owner’s guide says not to use water if grease is present because it could make the fire worse, and to use baking soda instead. Unplug the appliance if it is safe to do so, keep the door or drawer closed, and call emergency services if the fire does not go out. Use extreme caution when moving any appliance that holds hot oil, as the Ninja Foodi Grill owner’s guide warns.
What does work well
Air fryers do best with foods that crisp from a little oil and hot moving air. Try our easy air fryer donuts or air fried eggplant, or serve a snack like our green chile cheeseburger potato skins. If you also own a Ninja grill, our Ninja Foodi Grill guide covers that machine in more detail.
Clean it after every use
Mississippi State University Extension says to hand-wash the basket, tray and pan in warm soapy water after each use, soak baked-on grease first and wipe the interior with a damp cloth. Nebraska Extension says it is important to properly clean the basket or tray after each use. Mississippi State University Extension also warns that hard-to-clean parts can leave food particles behind for someone with food allergies. For leftovers you plan to reheat, see how long they last in our leftovers guide, and use a food thermometer to check that reheated leftovers reach 165°F throughout, the USDA minimum for leftovers.
Related reading
The same “check before you use it” logic applies elsewhere in the kitchen: see our lists of foods you should never microwave and things you should never put in the dishwasher, and our fire prevention tips for the rest of the house.
Air fryer questions, answered
Can you put aluminum foil in an air fryer?
It depends on the model and where you put it. The Ninja Prestige Smart XL owner’s guide prohibits covering the crumb tray or any part of the oven with foil and says not to cover the roast tray holes, but it allows lining accessories such as the sheet pan. Mississippi State University Extension does not address foil. Follow the placement rules for your exact model, and never let foil block airflow or touch the element.
See also
Can you use parchment paper in an air fryer?
Often yes, if your manual allows it. The Ninja Prestige Smart XL owner’s guide allows parchment as an exception to its ban on paper, and Nebraska Extension mentions baking cookies on parchment. Do not cover the vents or tray holes, and put food on the liner before the machine heats.
Can you use cooking spray in an air fryer?
Check your manual. Mississippi State University Extension says the additives in store-bought nonstick sprays can damage the basket, and the Ninja Prestige Smart XL owner’s guide says not to spray aerosols inside that oven while cooking. Tossing the food with a little oil, or using a refillable sprayer if your manual permits it, avoids the issue.
Can you cook raw chicken in an air fryer?
Yes, if you cook it to 165°F and verify with a thermometer, per Nebraska Extension. Raw frozen breaded stuffed chicken products are the exception: the CDC advised an oven for those.
Can you put glass or a baking dish in an air fryer?
Sometimes. Nebraska Extension says baking is possible with extra equipment such as glass baking dishes and muffin tins that fit inside the basket. The dish must fit without touching the heating element, be oven-safe at the temperature you use and be permitted by your manual. The Ninja Prestige Smart XL owner’s guide also urges extreme caution with containers made of anything other than metal or glass.
Can an air fryer catch fire?
Yes. Air fryers can catch fire because of defects or unsafe use. The U.S. Consumer Product Safety Commission recalled about 2 million COSORI units in 2023 for a wire connection that could overheat. Keep the unit clear of walls and flammable items, do not cover the vents, and stop using a recalled model.
How much space does an air fryer need around it?
It varies by model. Mississippi State University Extension says 5 inches behind the unit. Ninja’s guides say at least 6 inches on the Foodi Grill and at least 1 inch on the Prestige oven. Check your own manual.
How often should you clean an air fryer?
After every use, per Mississippi State University Extension and Nebraska Extension. Let the basket cool, wash it with warm soapy water, and wipe the interior.
Can you cook popcorn in an air fryer?
We do not recommend it, though this is our editorial advice and not a documented ban. Loose kernels can scatter in the basket, and the Ninja guides we checked do not mention popcorn. Check your manual if you want to try.
The bottom line
The real dangers are few and specific: raw breaded stuffed chicken that never reached 165°F, sprays with additives that can damage the basket, liners or foil that block airflow, a crowded basket, smoking oil, water on the base unit, metal tools, and a recalled machine or one pushed against a wall. Use a thermometer, give the unit room, clean it after each use, and treat your own manual as the final word.
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Source: Better Living – onbetterliving.com
