Automakers are warning that "smart" air bags required starting next year could kill or injure children and fail to protect adults in crashes. At least three suppliers have pulled smart-bag technology off the market for more development. One of them, Siemens, says it doesn't have any system that can't be fooled if an occupant shifts around in the seat or a child is in a heavy child seat, and doubts whether anyone else does. Automakers are searching for new suppliers, but doubt that the few remaining can make enough foolproof smart systems. As a result, what are billed as safety devices could be harmful.The bags, required by the National Highway Traffic Safety Administration, are called "smart" because they are supposed to sense what size passengers they're protecting, and adjust inflation force accordingly. The bags are supposed to turn off and not deploy if the passenger is a child. Earlier bags inflated full-force for everyone. As a result, at least 215 people, including 133 children, have been killed by air bags since 1990. Currently, NHTSA has refused to halt the phase-in of smart bags, beginning next September on 2004 models.