DIAGNOSIS Grease and food particles get aerosolized and stick to the top housing and the heating element guard. It's normal, but needs careful cleaning to avoid smoke or smells later.
FIX The key is to clean while the grease is still slightly warm, but with the unit unplugged and cool enough to touch. 1) Use a soft-bristled brush (a dedicated dish brush or even a clean paintbrush) to gently dislodge any loose crumbs from the heating element and the metal guard around it. 2) For the greasy top surface, make a paste of baking soda and a little water. Apply it with a damp cloth or sponge, let it sit for 10 minutes, then wipe away. The baking soda cuts the grease without harsh chemicals.
IF THAT DIDN'T WORK For stubborn, baked-on grease, you can try a dedicated non-abrasive oven cleaner, but spray it onto your cloth first, not directly into the fryer. Wipe thoroughly and run the fryer empty for 10 minutes afterwards to burn off any residue.
HEADS UP Never, ever immerse the main unit in water or run it under the tap. Don't use metal scouring pads or abrasive cleaners on the non-stick interior—you'll scratch it.