Any loose, hanging collar-- especially chain collars--can spell disaster. Any time two dogs play together if one or both are wearing loose collars they can get tangled and the result can be catastrophic.
Dogs like to playfully grab each other by the neck. When a collar is loose it is only a matter of time before a playful dog gets his jaw underneath that collar. If the dog wearing the collar twists around, the collar will become locked onto the grabbing dog’s lower jaw. When this happens, both dogs panic and try to get away only to tighten the collar further. This causes the dog wearing the collar to potentially choke to death and the other dog to break his jaw. Do not allow your dog to become a statistic. Tighten your dog’s collar. Remove chain collars, and request other dog owner’s to do the same.