The Beirut Explosion. Here’s What We Know

Ammonium nitrate the probable cause.

An explosion in Beirut creates a scary reminder of a nuclear bomb’s mushroom cloud – except for its pinkish color. Picture taken a moment before the resulting pressure wave devastates much of the city. (Picture courtesy of Business Insider)

It is Tuesday evening, and Beirut, the capital of Lebanon, is cooling from the day’s high of 86 degrees F (30 degrees C). Cell phones are held up to record a fire raging in the port when the sound of an explosion is heard. As everyone wonders what that was, there is a second, much bigger explosion. A massive pink cloud erupts from the ground. Then, a moment later, a simultaneous thundering boom. Videos go haywire as a shock wave rips the cell phones from people’s hands and knocks them over.

Video from security camera reveals the shock wave, visible as white round shape, bursting from the scene, like a deadly cotton boll from its seed, withering buildings as it spreads across city blocks — until that camera is knocked out of commission.

We had a few questions. And some answers.

What caused the explosion?

The likely cause: a deadly proximity of fireworks and ammonium nitrate. A Russian ship detained 6 years ago had its holds emptied of ammonium nitrate and 27,500 metric tons of it were being stored at the port.

The pinkish cloud is characteristic of an ammonium nitrate detonation.

What was the sequence of events?

  • T-6 years. A Russian ship carrying load of ammonium nitrate is detained by Lebanese port authorities.
  • T-14 minutes. Tuesday, Aug 4, 5:54 pm local time, a fire is reported in
    a port warehouse on Twitte

    Reports mention the presence of fireworks. “You can see in the center of the fire, you can see sparks, you can hear sounds like popcorn and you can hear whistles,” says Israeli explosive expert Boaz Hayoun to the Associated Press. “This is very specific behavior of fireworks, the visuals, the sounds.”

  • T -35 seconds, there is the first explosion.
  • T-0, 6:08pm, there is 2nd, much bigger blast.

What is ammonium nitrate?

Ammonium nitrate, NH₄NO₃, is the Jekyll and Hyde of industrial chemicals. It is usually shipped as prills (little porous pellets). It is odorless. Most of it (78%) is used as fertilizer and its cost and quantity produced make it one of the most widely used fertilizers on Earth. The remaining 22% is mixed with fuel oil to make explosives, mostly for industrial use. Ammonium nitrate is, by itself, not combustible, but it does act to support combustion.

The bomb used in the 1995 Oklahoma City bombing used two tons of ammonium nitrate and killed 168 people, including many children in a day care center in the Federal Building which it destroyed.

Ammonium nitrate's usual form: little porous pellets known as

Ammonium nitrate’s usual form: little porous pellets known as “prills.”

How dangerous is ammonium nitrate to store?

Under cool and dry conditions, ammonium nitrate is stable and safe. Up to 446 degrees F, it decomposes gently, giving off nitrogen (good for plants), water (vapor) and oxygen. At higher temperatures (500-572 degrees F), ammonium nitrate detonates.

How powerful was the Beirut explosion compared to a regular bomb?

The Beirut explosion was 20 times worse than the biggest bomb in the US arsenal, the GBU-43/B Massive Ordnance Air Blast, called “the mother of all bombs” after its first use against ISIS in Afghanistan in 2017 which as a blast yield of 11 tons of TNT.

Jeffrey Lewis, weapons expert at the Middlebury Institute of International Studies in California, estimates the Beirut explosion to be equivalent to “between 200 and 500 tons [of TNT], looking at blast damage, the shockwave, seismic signals, and the size of the crater.”

How does the Beirut explosion compare to Hiroshima?

The Beirut blast was significantly less powerful than the atomic bomb that devastated Hiroshima which was the equivalent of 15 kilotons of TNT.

The Beirut blast would be as powerful as a B61 nuclear gravity bomb, the smallest nuclear bomb in the US arsenal, which is equivalent to about 300 tons.

“The comparison ends there,” says Hans Kristensen, a nuclear weapon expert at the Federation of American Scientists in the Business Insider, reminding us that the pressure wave from a chemical reaction is slower and less destructive than the pressure wave from a nuclear reaction. Also, there is no nuclear fallout.