Unfortunately there isn’t, we can only assess the surface damage to the helmet and give our opinion. The shells are made to be very strong so a drop from a low height is usually fine, depending on the surface of course. The part of the helmet you can’t see is the EPS polystyrene liner; this absorbs energy during an impact, and as this is not removable there is no way of telling if the helmet has been damaged internally. Often you are the best person to make the decision on whether it’s safe to wear or not as you were there, we can only give our opinion – if in any doubt buy a new helmet!