what are the small black things that fall from top ceiling of my grill?
This answer is in regard to an outdoor Weber grille.  According to the Weber grille people the black peelings are carbonized grease that accumulate when cooking and are not harmful. They might not be tasty though so I recommend a quick wipe to loosen the particles before cooking.  Again Weber suggests using aluminum foil to brush the top and I believe that is because aluminum is softer than steel and so won't scratch the surface.  Happy grilling!