More like six years!
13:01
Officials 'asked for ammonium nitrate to be moved'
The highly explosive substance blamed for Tuesday's blast was meant to be moved, the port's general manager has told local broadcaster OTV.
Hassan Koraytem said the ammonium nitrate had been in the port for six years, following a court order.
But, despite instructions from the customs department and state secretary to move or export it, "nothing happened", he told the broadcaster.
https://www.bbc.co.uk/news/live/world-middle-east-53664184What caused the mushroom cloud?
Videos from Beirut showed smoke billowing from a fire, and then a mushroom cloud following the blast.
"You have a supersonic shockwave that is travelling through the air, and you can see that in the white spherical cloud which travels out from the centre, expanding upwards," says Prof Sella.
The shockwave is produced from compressed air, he explains. "The air expands rapidly and cools suddenly and the water condenses, which causes the cloud," he adds.
How dangerous is ammonium nitrate?
On its own, ammonium nitrate is relatively safe to handle, says Prof Sella.
However, if you have a large amount of material lying around for a long time it begins to decay.
"The real problem is that over time it will absorb little bits of moisture and it eventually turns into an enormous rock," he says. This makes it more dangerous, he adds, because it means if there is a shock, it will spread much more easily.
The longer it is left, the more likely it will get contaminated with items such as fuel oil, former senior military intelligence officer Philip Ingram told BBC Radio 4's Today programme.
Once that happens it can produce a reaction in the chemical. "It generates its own heat and, once it's started, it continues to generate it and that will build up over time," Mr Ingram says. "That could then lead to the high-order explosion that we saw in those horrific videos that came out of Beirut."
https://www.bbc.co.uk/news/explainers-53664064