Lessons Learned
The explosion at the Oppau plant is an example of the fallibility of inductive reasoning when health and safety are on the line. This thought process - that what worked in the past will work now and in the future - is not sufficient in potentially high-risk operations. When entering new territory (e.g. using new chemicals), it's never OK to assume things will still work the same without sufficient facts or tests to support these claims.
Though the workers at the site never got to learn for themselves, the Oppau disaster was a terrible revelation of the explosive power of ammonium nitrate. Unfortunately, many more ammonium nitrate explosions have followed in the years after Oppau. This includes the 1947 Texas City disaster, which might be the most infamous explosion involving ammonium nitrate; not to mention the deadliest industrial accident in U.S. history.