Cargo Hold Ventilation, Dew Point & Sweat Risk Tool

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Ambient Dew Point, Hold Dew Point, Cargo Sweat, Ship Sweat, Dew Point Rule & Three Degree Rule

Cargo Hold Ventilation, Dew Point & Sweat Risk Tool

Screen cargo-hold condensation risk using measured air temperature, relative humidity, cargo-surface temperature and steel temperature. The tool keeps current cargo sweat, current ship sweat and the effect of introducing outside air separate, then compares the Dew Point Rule and Three Degree Rule without pretending they are interchangeable for every cargo.

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Need multiple holds, ventilation capacity and hold-by-hold rule conflicts? Click Advanced above.Advanced calculates a separate dew point and sweat margin for each hold, plus air changes per hour and an idealized air-replacement time. It still does not override cargo-specific ventilation instructions.

Fast Sweat-Risk & Ventilation Screen

Exactly 10 primary inputs. Temperatures are in °C. Weather restriction is a screening gate only; cargo schedules requiring ventilation for gas or other hazards must be handled separately.

Outside / ambient air temperature°C.

Outside / ambient relative humidity% RH.

Hold air temperature°C.

Hold relative humidity% RH.

Cargo surface temperature°C at or near exposed cargo surface.

Internal steel / deckhead temperature°C representative cold steel surface.

Cargo temperature at loading°C, used by the Three Degree Rule.

Cargo moisture behaviour

Ventilation rule basis

Weather / sea-spray ventilation condition

Ambient & Operating Basis

Outside / ambient air temperature°C.

Outside / ambient relative humidity% RH.

Cargo moisture behaviour

Ventilation rule basis

Weather / sea-spray condition

Minimum dew-point improvement margin°C below hold dew point required before this tool marks the Dew Point Rule favourable. 0°C reproduces the usual ambient DP ≤ hold DP comparison.

Cargo Hold Register

Hold names are excluded from Tool Data and result tables. Ventilation capacity is used only for air-change planning, not to predict how fast cargo moisture or steel temperature will change.

Hold	Free air volume m³	Hold air °C	Hold RH %	Cargo surface °C	Steel / deckhead °C	Cargo loading °C	Ventilation capacity m³/h

Moisture / condensation screen only: this tool does not determine whether a cargo is legally or operationally permitted to be ventilated. Specific IMSBC schedules and shipper instructions may require ventilation, prohibit ventilation, or impose gas-monitoring / explosion-control requirements unrelated to sweat. Do not use this calculator to override those requirements or enclosed-space safety procedures.

Ventilation context: cargo sweat forms when cargo temperature is below the dew point of air in contact with it; ship sweat forms when internal steel is below the dew point of hold air. Industry guidance commonly applies the Dew Point Rule by ventilating when outside-air dew point is lower than or equal to hold-air dew point, weather permitting. The Three Degree Rule is another cargo-temperature-based method used for appropriate cargoes. The IMSBC Code remains the mandatory SOLAS-based code for solid bulk cargoes and contains cargo-specific ventilation instructions that take precedence over this generic sweat screen. IMO IMSBC Code · Gard Cargo & Ship Sweat Guidance

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