Yellow grain had been loaded in all cargo holds up to the hatch coverings by a bulk carrier. Fumigation technicians arrived on board after the loading was completed and fumigated the cargo using fumitoxin pellets.
The fumigation pellets were required to be placed subsurface, according to the shipment documents. The technicians poured the pellets from flasks while stepping on the hatch coverings or hatch comings in this case. After a little more than an hour of effort, all of the cargo hatches were closed and the ship was set to sail.
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An explosion happened in one of the holds a few hours later. The hatch covers had shifted somewhat, and blue-grey smoke could be seen pouring from beneath the edges, according to the crew. A third explosion occurred about an hour later in a second hold, and a fourth occurred a few minutes afterward. Shortly later, explosions erupted in the other holds.
Fumitoxin pellets and similar fumigants contain roughly 55% aluminum phosphide, which interacts with water to form phosphine, a very poisonous and powerful fumigant. When phosphorus gas is combined with air at a concentration of more than 1.8 percent to 2% by volume, it forms an explosive combination (the lower flammable limit).
In each of the holds, the phosphine content in the air surpassed the lower flammable limit. The fumigant pellets in each hold were not spread evenly throughout the cargo surface or applied to the subsurface; instead, they were simply poured on top of the cargo.
This technique of administration allowed the pellets to accumulate in small places and encouraged a relatively quick interaction of the pellets with moisture, resulting in phosphine gas concentrations beyond the lower flammable limit, resulting in the explosions.
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