Ferrosilicon: IMSBC Code Schedule and Carriage
The ferrosilicon schedules under the IMSBC Code: the silicon content bands, the class 4.3 and MHB split, and the arsine and phosphine entry limits of 0.05 and 0.3 ppm.
Ferrosilicon is the IMSBC Group B family that evolves toxic gas rather than heat. On contact with moisture the alloy releases hydrogen, and where the alloy carries arsenic or phosphorus impurities it also releases arsine and phosphine, both lethal at parts-per-million concentrations. The Code splits the cargo across schedules on silicon content, with one entry carrying class 4.3 with subsidiary hazard 6.1 and another carrying the MHB notation WF and/or WT.
The full article will cover both ferrosilicon entries and ALUMINIUM FERROSILICON POWDER UN 1395, which requires a detector covering four gases including silane and two sets of self-contained breathing apparatus over and above the SOLAS regulation II-2/10.10 fire-fighter’s outfits. It will set out the shared appendix in detail: at least two separate explosion-proof fans giving 6 air changes per hour on an empty cargo space, running from commencement of loading until the space is free of cargo; monitoring at least once every 8 hours at each outlet ventilator and in any accessible adjacent space, and at 30 minute intervals while anyone is inside; and the entry prohibition above 0.3 ppm phosphine, above 0.05 ppm arsine, or below 18 percent oxygen.
It will also carry the clinical point the appendix records and most guidance omits: arsine poisoning generally shows a delay before onset, sometimes of a day or so, the early symptoms are indefinite, and severe anaemia and jaundice can appear after a day. A crew member who feels well has not thereby escaped an exposure.