Lifter01 being from West Yorkshire im sure you will be aware of a little place called Halifax. In Halifax down by the Train station is Nestle. Now Nestle use ammonia and as you have pointed out ammonia leaks and kills people, so I have asked some one I know who works at Nestle about ammonia leaks and deaths. His reply was he has work at Nestle for over ten years and doesn't know of any leaks or any being killed from leaking ammonia. He did say there is a safety procedure to follow but he has never known it be used.