Cargo Hold Ventilation & Sweat Risk Tool

Dew Point Rule • Three Degree Rule • Ship Sweat • Cargo Sweat • Humidity Ratio • Air Changes • Moisture Export • Multi-Hold Plan

Cargo Hold Ventilation & Sweat Risk Tool

Turn cargo-hold and weather readings into a defensible ventilation decision. Simple mode compares outside and hold dew points or applies the Three Degree Rule while separately screening ship sweat and cargo sweat. Advanced evaluates multiple holds, cargo profiles, steel and cargo temperatures, ventilation capacity, cargo-specific instructions and live ventilation windows without overriding the applicable IMSBC schedule, shipper instruction, fumigation requirement or vessel procedure.

↑

For several holds, fan capacity or cargo-specific restrictions, click Advanced above.Weather safety is a hard gate. If rain, heavy spray or sea conditions make ventilation unsafe, the tool suspends the generic sweat-control recommendation.

DecisionVentilate / hold / suspend

CondensationShip & cargo sweat margins

Air qualityDew point & humidity ratio

Ventilation Rule & Weather

Decision rule

Weather safe for ventilation?

Outside dry-bulb temperature°C.

Outside relative humidity

Atmospheric pressurekPa absolute.

Hold & Cargo

Hold air temperature

Hold relative humidity

Average cargo temperature at loading°C. Used by Three Degree Rule.

Current cargo surface temperature°C. Used for cargo-sweat screen.

Hold steel / hatch-cover temperature°C. Use measured value where possible.

Outside Air & Watch Basis

Generic decision rule

Outside dry-bulb temperature

Outside relative humidity

Atmospheric pressure

Sea temperature

Weather / opening condition

Theoretical ventilation air densitykg dry air / m³ approximate.

Cargo Hold Register

Cargo-specific ventilation instructions control. “Mandatory / cargo instruction” means the generic sweat rule is shown for awareness but cannot cancel the entered cargo requirement. “No ventilation” similarly overrides the generic sweat rule.

Use	Cargo profile	Instruction	Hold T °C	Hold RH %	Loading cargo T °C	Current cargo T °C	Steel T °C	Hold volume m³	Vent flow m³/h

Ventilation / Cargo Checks

Cargo schedule / shipper instruction checkedIMSBC, Grain Code, fumigation or commodity-specific requirements have priority. Hold readings representativeMeasurements are taken away from ventilation inlets. Outside readings representativeAmbient readings are not contaminated by exhausts or spray. Cargo loading temperature loggedThree Degree Rule uses average cargo temperature recorded during loading. Steel / hatch condition inspectedVisible sweat and cold surfaces are considered with calculated margins. Weather openings safeRain, spray and heavy weather cannot introduce water into the cargo space. Ventilation system availableFans, vents and closures are operating as intended. Ventilation log maintainedReadings, rule, start/stop times and reasons are recorded each watch.

Operational limitation: the Dew Point Rule and Three Degree Rule are general cargo-sweat/ship-sweat management methods. They do not override mandatory ventilation or sealing instructions for a particular cargo, fumigation requirements, dangerous-gas controls, oxygen-depletion precautions, shipper instructions or vessel procedures. Some IMSBC schedules require continuous or controlled mechanical ventilation for hazards unrelated to condensation.

Ventilation basis: the Dew Point Rule says ventilate when hold-air dew point is higher than outside-air dew point and do not ventilate when hold dew point is lower. When reliable hold dew point cannot be obtained, the Three Degree Rule says ventilate when outside dry-bulb temperature is at least 3°C cooler than the average cargo temperature at loading. Weather permitting remains a necessary operational gate, and cargo-specific mandatory instructions remain controlling.

Generated by ShipUniverse.com

By the ShipUniverse Editorial Team — About Us | Contact