Start with the cargo, not a rule of thumb

Ventilation is not a simple choice between “open” and “closed.” For a bulk voyage, the decision depends on the cargo’s properties, the conditions inside the hold, the outside air and the weather. Before applying a moisture-control rule, check the cargo information and the relevant cargo schedule. The IMSBC Code provides cargo-hazard information and instructions for safe stowage and shipment; its requirements are the starting point when the cargo presents a specific hazard. ([imo.org](https://www.imo.org/en/ourwork/safety/pages/cargoesinbulk-default.aspx?utm_source=openai))

That distinction matters because ventilation can serve purposes other than controlling condensation. For example, the IMSBC Code text addresses ventilation where cargoes may emit toxic or flammable gases, and says that cargo-specific instructions may require continuous ventilation. A moisture-control shortcut should never override a cargo-specific ventilation requirement. Conversely, ventilation may need to be interrupted if continuing it endangers the ship or cargo, subject to the conditions described in the Code. ([wwwcdn.imo.org](https://wwwcdn.imo.org/localresources/en/KnowledgeCentre/IndexofIMOResolutions/MSCResolutions/MSC.462%28101%29.pdf?utm_source=openai))

Resolution MSC.462(101): Amendments to the International Maritime Solid Bulk Cargoes (IMSBC) Code · International Maritime Solid Bulk Cargoes (IMSBC) Code

Know which kind of “sweat” you are trying to prevent

Cargo sweat forms when air in contact with cargo is cooled below its dew point, so moisture condenses on the cargo. One risk is introducing warm, moist outside air into a hold containing colder cargo. Ship’s sweat is different: it forms on cool steel surfaces inside the hold when the air’s dew point is higher than the steel temperature. Droplets can then reach cargo beneath the deckhead or stowed against the ship’s sides. The two mechanisms point to different risks; simply ventilating more is not automatically safer. ([gard.no](https://gard.no/en/insights/dont-work-up-a-sweat/?utm_source=openai))

A route’s changing conditions make the decision less obvious than a slogan such as “warm to cold, ventilate.” A voyage may cross several climatic regions, and outside air that is useful at one stage may add moisture later. Gard describes the dew-point rule as a practical guide: ventilate only when the ambient-air dew point is no higher than the hold-air dew point. Rain, snow, fog or mist are also reasons not to ventilate under that guidance. Treat the rule as a moisture-control aid—not a substitute for cargo-specific instructions or the Master’s assessment of conditions. ([gard.no](https://gard.no/en/insights/dont-work-up-a-sweat/?utm_source=openai))

Don't work up a sweat!

Make the decision a repeatable check

A useful routine is to consider four questions before ventilation: What does the cargo schedule or shipper’s information require? Is the concern cargo sweat, ship’s sweat or a separate cargo hazard? Are the ambient and hold-air dew points suitable for the intended ventilation? Could rain, fog, spray or the ship’s operating conditions make ventilation unsafe? This sequence turns a vague instruction to “ventilate when needed” into a reasoned decision tied to the cargo and conditions. ([gard.no](https://gard.no/en/insights/dont-work-up-a-sweat/?utm_source=openai))

If different holds carry cargoes with different ventilation needs, check that the planned arrangement can serve them appropriately. Gard notes that holds may have individual or common ventilation arrangements, and that care is needed when cargoes with different requirements are carried in different holds. In adverse sea conditions, the risk of spray entering ventilation openings is another reason to stop ventilation and close openings, according to the same guidance. ([gard.no](https://gard.no/en/insights/dont-work-up-a-sweat/?utm_source=openai))

Don't work up a sweat!

Keep a record that explains the choice

Record when ventilation took place and why; also note periods when it could not be carried out, such as because of unsuitable weather. A record is most useful when it lets a later reader follow the decision, rather than merely showing that a fan was switched on. Where dew-point comparison is the basis, record the readings and the resulting choice. Gard highlights ventilation records as important evidence when moisture damage is alleged. ([gard.no](https://gard.no/en/insights/dont-work-up-a-sweat/?utm_source=openai))

Observations in the hold can add context, but inspections should only be made when it is safe to enter. If signs of condensation appear, record where they are seen and relate them to the ventilation and weather history. For cargoes that may emit hazardous gases, apply the applicable monitoring and ventilation controls; a visual moisture check cannot establish that an atmosphere is safe. The practical goal is not to ventilate continuously by habit, but to follow the cargo’s requirements, improve the hold-air conditions when appropriate, and be able to explain the decision afterward. ([gard.no](https://gard.no/en/insights/dont-work-up-a-sweat/?utm_source=openai))

Don't work up a sweat! · Resolution MSC.462(101): Amendments to the International Maritime Solid Bulk Cargoes (IMSBC) Code