What is the IMSBC Code, and what are MHB materials?
Short answer
| MHB hazard (§9.2.3) | Code | Below the IMDG class |
|---|---|---|
| Combustible solids | CB | 4.1 |
| Self-heating solids | SH | 4.2 |
| Solids evolving flammable gas when wet | WF | 4.3 |
| Solids evolving toxic gas when wet | WT | — |
| Toxic solids | TX | 6.1 |
| Corrosive solids | CR | 8 |
- IMSBC Code: mandatory under SOLAS chapter VI for solid bulk cargoes; a schedule per cargo and the shipper’s declaration before loading (SOLAS VI/2).
- Three groups: A may liquefy above the transportable moisture limit (TML, §8 tests); B chemical hazard; C neither.
- Group B: either IMDG dangerous goods (§9.2.2, e.g. bulk ammonium nitrate, class 5.1) or MHB (§9.2.3).
- MHB, materials hazardous only in bulk (§9.2.3): a chemical hazard only in bulk, below the IMDG class criteria: combustible (CB), self-heating (SH), flammable gas when wet (WF), toxic gas when wet (WT), toxic (TX), corrosive (CR).
- Precautions: ventilation, gas and oxygen monitoring, fixed fire-fighting (§13.2.3, SOLAS II-2/10.7), enclosed-space entry controls, segregation of incompatible Group B cargoes (§9.3), the Document of Compliance.
- As Chief Engineer: hold ventilation, gas and oxygen monitoring, fixed fire-fighting and bilge pumping are mine; the cargo dictates them.
Full answer
The full answer explains each point step by step, with the regulations and figures behind it and the discussion from other candidates. It is in the MEO Class I section of the Marine One forum, open to members enrolled for the MEO Class I exam.