There are instances when an air fryer catches fire, but they are rare. Two specific issues can lead to an overheated unit bursting into flames. The first relates to how the machine operates when cooking food. Oil is needed in an air fryer to cook anything (without oil, the heat would be too high for cooking something like French fries). When the user overfills the unit with oil or leaves cooking oil inside after cleaning out other residues (like bread crumbs), the problem occurs.