This enforcement action was filed in response to an anhydrous ammonia release which occurred at the Logansport facility on 4/28/2008. Tyson employees decided to purge air from their system by opening valves. They had assumed that most of the purge gas would be air and not ammonia and that the purge process would be of short duration. They vented the system for over 7 hours - releasing 3,923 lbs of ammonia (39 times the RQ). Notifications to the NRC, Indiana SERC and their LEPC were done over 4 hours after knowledge of the release.