[Edwina Lee (OP)]

Ammonium nitrate (NH₃ N0₄) Beirut explosion videos.
TV in  Hong Kong said it was caused by heat.
(1) what on earth are those white bands at the beginning of the BBC video? https://twitter.com/BBCWorld/status/1290720709623320583?s=19
(2) what is the explosion's chemistry?

[Edwina Lee (OP)]

Looks like the white rings are added artwork to the video.
This BBC article has the video without the rings at the beginning.
https://www.bbc.co.uk/news/amp/world-middle-east-53656220?__twitter_impression=true

[Bored chemist]

Looks like the white rings are added artwork to the video.
This BBC article has the video without the rings at the beginning.
https://www.bbc.co.uk/news/amp/world-middle-east-53656220?__twitter_impression=true

What are you on about?

The clouds are real.
It would be silly to add them.

They are present in all the videos, (about 8 seconds into the 2nd vid, for example) though they are clearer in some than in others.

They form because the air immediately behind the shockwave expands rapidly and cools, causing moisture to condense from the air.
You don't need an explosion to see the effect- it's part of what causes condensation trails behind aircraft.
https://en.wikipedia.org/wiki/Vapor_cone

The explosion is mainly NH4NO3 --> H2O + N2 + O2
 The O2 released reacts with any oxidisable impurities in the material which increases the heat released.
Some NO and NO2 are produced too
NO2 is brown, and you can see that in the cloud.

[evan_au]

The first video had a white spiral BBC logo added at the start.
- But the white clouds behind the shockwave are real in all the videos.

Some other videos I have seen showed a fire in a fireworks warehouse. The people seeing the fireworks seemed to think this was quite entertaining - quite unlike the massive explosion that appeared to be triggered by the fireworks.

Chemists on TV tonight said that you have to get Ammonium Nitrate quite hot before it explodes - so fireworks should probably not be stored next to  Ammonium Nitrate!

[Bored chemist]

vid clip.png (203.33 kB . 497x504 - viewed 796 times)

The first video had a white spiral BBC logo added at the start.

Here's the start of the vid.
The Beeb's logo is there later but... well, it's their logo; they plaster it all over the place.

[evan_au]

Another interesting artifact is the "mouth" in the white cloud behind the shockwave.
- It grows faster than the speed of sound to eat Beirut...

Is it possible that the shockwave was attenuated or diffracted by the hot smoke of the prior fireworks show?

[Edwina Lee (OP)]

The first video had a white spiral BBC logo added at the start.
- But the white clouds behind the shockwave are real in all the videos.

Some other videos I have seen showed a fire in a fireworks warehouse. The people seeing the fireworks seemed to think this was quite entertaining - quite unlike the massive explosion that appeared to be triggered by the fireworks.

Chemists on TV tonight said that you have to get Ammonium Nitrate quite hot before it explodes - so fireworks should probably not be stored next to  Ammonium Nitrate!

It makes sense now, thanks. Fire at the fireworks storage caused the big explosion.
So sad that the Judge for Urgent Matters failed to do anything to get rid of the fertilizer for so many years, so this should all be totally avoidable.
 The current story:-
https://www.bbc.com/news/world-middle-east-53668493?intlink_from_url=https://www.bbc.com/news/topics/c88p951myv0t/beirut-port-explosion&link_location=live-reporting-story
https://www.bbc.com/news/world-middle-east-53683082
https://edition.cnn.com/2020/08/05/europe/lebanon-russian-ship-blast-intl/index.html

[Edwina Lee (OP)]

Another interesting artifact is the "mouth" in the white cloud behind the shockwave.
- It grows faster than the speed of sound to eat Beirut...

Is it possible that the shockwave was attenuated or diffracted by the hot smoke of the prior fireworks show?

I think the mouth was created by the presence of the tall building.
As bored chemist explained that the white cloud is the vapor trail of the explosion. As the shock wave expand in a bubble fashion, the molecules are propelled away from the centre forming a low pressure area behind the shockwave thus forming the vapor. As the tall building is in the way, the volume of air behind the building is pressurised into an elipsoid volume, thus failing to form the vapor until after passing the building hence the mouth shape.
The moment of explosion:-
https://www.bbc.com/news/av/world-53657745/beirut-blast-city-explosion-causes-widespread-damage