DSS102: Review of the Beirut Port Explosion with Dr. Suzanne Smyth and Dr. Russell Ogle

In this episode of the Dust Safety Science podcast, Dr. Suzanne Smyth and Dr. Russell Ogle, from Exponent‘s Thermal Science Practice, are both returning to talk about a massive explosion that took place near the port of Beirut in Lebanon on August 4, 2020. Over 200 people were killed and thousands were injured in the incident, which was traced back to the improper storage of over 2500 tons of ammonium nitrate.

Both Russell and Suzanne are very involved in fire, explosion, and chemical safety incident investigations. Dr. Ogle, whose background in combustible dust and related hazards spans over 30 years, authored the textbook Dust Explosion Dynamics. Today, they discuss the circumstances of the Beirut port explosion and answer the following questions:

How are large-scale incidents like this investigated?
Is there any general consensus of the sequence of events that occurred in Beirut?
What caused the explosion to be so large?
Are there guidelines for spacing inside these storage facilities?
Was the grain silo involved in any way?

How are large-scale incidents like this investigated?

Suzanne explained that all explosion investigations start in a similar manner. Once the problem is defined, the next step is to gather information. In the case of the port explosion, this information has only been available through the news media, which cannot be independently verified.

She said that when looking at an explosion of this size, the first step is to understand all relevant circumstances. What is the layout of the land? What was stored nearby? What was stored where the incident may have occurred? What witness information can you get? Videos are incredibly helpful when establishing timelines and sequence of events. What happened first? What happened second?

“Once you have enough information to start, you start hypothesizing about what could have happened and then, following the scientific method, your goal is to refute those hypotheses,” Suzanne said. “So, for instance, if there was a hypothesis that this was a dust explosion, you could try and say, “Well can we prove it definitely wasn’t a dust explosion?” And that could knock that hypothesis off the list.”

When an explosion investigation is the issue, it’s important to determine what the fuel, oxidizer, and ignition sources were, and how those three might have worked together to create the incident.

“What I find most helpful in a large event is trying to bound things,” she explained. “There was this type of severe damage X distance away from the epicenter. So how much fuel, or what size of explosion would we need to cause that? Now you have an outer bound, or a minimum bound, and you can start trying to chop off the ends and get narrower and narrower as your analysis, the science, and facts allow.”

Is there any general consensus of the sequence of events that occurred in Beirut?

Suzanne said that based on the videos she saw, the incident appears to have been a fire that led to an explosion. The sequence of events also appears to be known, and information is available about the timeline of ammonium nitrate storage at the port.

“I’ve seen some reports regarding ignition sources,” she added. “There were reports of hot work in the area. There were some reports of other hazardous materials and flammable materials being stored nearby. I certainly haven’t seen yet a consensus of the ignition event.”

Russell said that according to the news media, there were approximately 2700 metric tons of ammonium nitrate stored in super sacks in the warehouse. When ammonium nitrate spontaneously and suddenly decomposes, it can resemble a detonation, with an energy yield of about 50%. This amounts to about 1000 tons of TNT.

There were two damage features that he found to be very distinct. The first was the window breakage. The second was a huge crater, which is normally seen with condensed phase deflagration or detonation. In both cases, the ballpark energy yield appeared to be approximately 1000 tons of TNT.

“Now, in a typical dust explosion, you would come nowhere near one metric ton of TNT in terms of an energetic yield,” he said. “It would be a very, very small fraction of a ton. And admittedly, this is a very imprecise comparison, because a dust explosion typically is a deflagration. It’s a very different phenomenon compared to a condensed phase detonation. But if we try to look at this in terms of the energetic yield, a dust explosion would be so much milder. What happened in Beirut is, for lack of a better phrase, several orders of magnitude worse than what you could get with a dust explosion.”

What caused the explosion to be so large?

Russell pointed out that ammonium nitrate is a powerful oxidizer and can feed some kind of combustion process. When it mixes with organic material, the result is an intimate mixture of fuel and oxidizer. Ammonium nitrate also has a shelf life when exposed to temperature cycles like those in Beirut: its crystal structure changes and it becomes more porous.

“Large quantities of ammonium nitrate were aged in a bad way in terms of temperature cycling and exposure to humidity,” he explained. “And then if the photographs that we’ve seen of the warehouse are indeed accurate and portray the storage conditions of the ammonium nitrate, it was a dirty storage area. And any debris or dirt could be potentially organic, and that’s going to contribute to the problem.”

Are there guidelines for spacing inside these storage facilities?

According to Russell Ogle, different safety standards have been developed by different bodies around the world. In the United States, the National Fire Protection Association, or NFPA, has a document for hazardous materials called NFPA 400.

“The threshold quantity below which you don’t have to really worry about the storage of ammonium nitrate is approximately one half of a ton,” he said. “So if you have more than half of a ton, then you need to look at these special storage requirements.”

He added that after the initial blast, a large plume of reddish brown material rose into the air. The color is a characteristic feature of nitrogen dioxide, which is one of the decomposition products of ammonium nitrate.

“I think it underscores that clearly, along with the explosion damage, the quantity of material, and this reddish brown plume, it’s the ammonium nitrate that was really the bad actor in this incident.”

Conclusion

“One of the big takeaways from an event like this (is that) we’re so hungry for information right after the incident because you want to know what happened, you want to understand it,” Suzanne said. “(However), these types of investigations which, if done properly, take time. It takes time to vet the information. It takes time to analyze it. Sometimes taking a step back and waiting for quality information is helpful before jumping to some conclusions. That’s part of the scientific method as well, right? You want good, quality information to base your analysis on.”

If you would like to discuss further, leave your thoughts in the comments section below. You can also reach Suzanne Smyth and Russell Ogle directly:

Suzanne:
Email: [email protected]
LinkedIn: https://www.linkedin.com/in/suzy-smyth-b384298/

Russell:
Email: [email protected]
LinkedIn: https://www.linkedin.com/in/russell-ogle-590554a3/

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