#Beirut explosion: What is ammonium nitrate (NH4 NO3), and why is it so dangerous?
A short thread by @PeterRNeumann and @blumscientific, PhD biochemist and former head of OPCW laboratory. 1/

Ammonium nitrate is a highly combustible salt (the ammonia salt of nitric acid), which is normally used as agricultural fertiliser -- often mixed with other salts or additives. 2/

However, because of its combustible nature and widespread availability, ammonium nitrate has also become a popular ingredient for "home-made bombs". 3/

For decades, "truck bombs" by terrorists have frequently involved large amounts of ammonium nitrate. With devastating results. Examples include the first World Trade Center bombing in 1993, and the Oklahoma City bombing in 1995. 4/

Another example is Anders Breivik's 2011 bombing of a government building in Oslo. Preparing for the attack, Breivik had rented a farm and bought large amounts of fertiliser, which he said he needed for agriculture. 5/

To turn it into an explosive, ammonium nitrate is often mixed with fuel oil (ANFO). But in certain conditions, it can react with itself. Many governments have therefore imposed stringent rules for safe storage, and restricted its purchase. Example: UK government guidance 6/

Contrary to Trump's statement yesterday, there is *zero* evidence that the #Beirut explosion was caused by a bomb (see pictures). Far more likely: it resulted from the unsafe storage of what the Lebanese government says was a massive amount (2,750 tons) of ammonium nitrate. 7/

The #Beirut explosion echoes a 1921 incident at a BASF factory in Germany, where 400 tons of ammonium nitrate exploded. The incident sparked rumors about attacks and "secret weapons" experiments. None of them turned out to be true. More here: https://twitter.com/blumscientific/status/1290920155980193793?s=19 8/

#Beirut explosion may turn out to be a *monumental* case of negligence. Storing (1) such a massive amount of ammonium nitrate; (2) in humid conditions (which makes it coalesce into solid mass, increasing its potency); and (3) over such a long period time = recipe for disaster 9/