This question already has an answer here:
Most advice on cast iron pan care says that most of the time you shouldn't use soap when washing a pan. However, that may leave some residual fat/grease from your cooking on the pan.
It can be fat/oil with a low smoke point which is going to smoke then next time you heat the pan.
Would it be safe to cook in such smoking pan? Should you burn it till it stops smoking? Is this smoke in the kitchen safe for your lungs?