Arsine and Phosphine in Solid Bulk Cargoes

Arsine and phosphine are the two gases most often responsible for toxic-atmosphere fatalities in bulk carrier cargo spaces, and they reach a hold by two entirely separate routes that are frequently confused. The first is chemical: ferrosilicon and aluminium ferrosilicon carrying arsenic and phosphorus impurities evolve both gases on contact with moisture. The second is deliberate: aluminium phosphide fumigant tablets applied to an agricultural cargo decompose in humid air to release phosphine.

The full article will separate the two mechanisms and their controls. On the chemical route it will cover the IMSBC ferrosilicon appendix figures, which are among the very few occupational concentrations the Code states in its own text: entry prohibited above 0.3 ppm phosphine, above 0.05 ppm arsine, or below 18 percent oxygen, with a note that arsine at 250 ppm is dangerous to life after 30 minutes and at 6.25 to 15.5 ppm after 30 to 60 minutes. On the fumigation route it will cover IMSBC section 3.6 and its eight-hour interval gas concentration checks.

It will also cover the two properties that make both gases exceptional for a practitioner. Onset is delayed, sometimes by a day, and the early symptoms are indefinite, so absence of immediate effect is not evidence of a safe exposure. And the recommended exposure limits sit far below portable detector resolution, which is why the practical control on these cargoes is exclusion and ventilation rather than measurement.