Neodymium magnets are extremely powerful. Crushing and bruising injuries can occur when handling these magnets, especially the larger ones. When two magnets collide together, small pieces can be broken off and cause injury. For these reasons the magnets should be handled carefully and they should definitely not be allowed to crash into one another from a distance. Magnets should never land in children’s hands because swallowing them can lead to serious medical problems.
Particularly the larger neodymium magnets should never be stored or used near devices or objects that can be damaged by magnetism. This can include, among others, televisions and monitors, credit cards, bankcards, computers, data storage devices of all kinds, video and music cassettes, mechanical clocks and speakers. A large magnet can also disturb heart pacemakers. When in doubt you should exercise caution!