According to the National Transportation Safety Board (NTSB), the recent rupture of an anhydrous ammonia tank in Iowa, which killed one worker, was due to inadequate welding, insufficient inspection during the tanks manufacture and lack of periodic inspections during its service life. The NTSB concluded periodic non-destructive testing could have detected the defect and the internal crack in the tank during its service life and the tank could have been repaired or removed from service. The NTSB has now recommended all nurse tanks undergo nondestructive testing to identify flaws that could lead to a rupture. Currently there are no federal or state requirements concerning periodic inspections be conducted.