Preventing container condensation in bulk tea requires control of the whole moisture system, not simply hanging a guessed number of desiccant bags. Define the tea and pack, map the route and temperature changes, verify product and dunnage are dry to agreed criteria, inspect a clean and weather-tight container, calculate any moisture-control capacity, protect packages from possible drip paths, document loading and seal condition, and inspect the arrival before evidence is disturbed.

Why apparently dry tea can still face container rain

A closed freight container develops its own internal climate. Water vapour can enter with the tea, cartons, timber, pallets, humid loading air or rain during packing. When warm moist air or a moisture-releasing cargo meets a sufficiently cold roof or wall, the air at that surface can reach its dew point and water can condense. Later warming can move moisture again. A single pre-loading relative-humidity reading therefore does not describe a multi-week route.

The joint IMO/ILO/UNECE Code of Practice for Packing of Cargo Transport Units identifies cargo, porous packaging, timber and wet or humid packing conditions as moisture sources, and tells packers to consider foreseeable climatic impacts. It also warns that plastic wrapping may worsen mildew or water damage when total moisture is already too high, and that drying-agent capacity should be calculated rather than assumed.

Separate the five requirement layers

  • Legal requirement: food, packaging, wood-treatment, container, carrier, customs and destination rules may impose binding duties. The CTU Code does not replace them.
  • Voluntary standard or code: the CTU Code is a non-mandatory global code of practice. ISO 11287:2011 is a current voluntary green-tea standard that also covers packing and marking; ISO 2233:2000 is a current method for conditioning filled transport packages and unit loads for testing.
  • Trade reference: phrases such as "dry container," "export packing," "moisture proof" or "ten desiccant poles" are useful conversation starters, not complete acceptance rules.
  • Buyer specification: the buyer states the product, route assumptions, packaging system, container checks, moisture controls, loading evidence and arrival decision method.
  • Contract requirement: the signed agreement allocates who approves the container and controls, who pays, what evidence is required, when risk transfers, and how wetting or damage is handled.

Status checked 24 August 2026: IMO's list of current publications dated 22 June 2026 still lists the CTU Code, 2014 Edition. UNECE has circulated a "2025 revision" as a working document for its 69th WP.24 session. Buyers should not silently treat that working text as an adopted legal or contractual replacement; name the exact edition used.

Write a route-to-release control sheet

Control fieldBuyer should defineEvidence to retain
Tea and lotStyle, lot, pack date, agreed moisture method and limit, approved sampleLot record, COA and representative sample record
Packaging systemInner liner, seal, outer pack, pallet and moisture-sensitive componentsApproved specification, pack codes and closure checks
Route profileOrigin season, port dwell, sea or rail legs, transshipment, destination and expected durationBooking, route assumption and available logger history
CTU acceptanceCorrect type, clean, dry, odour-free, sound roof/walls/doors/floor and acceptable prior-cargo evidenceDated checklist and photographs before loading
Moisture planDry-loading rule, dunnage condition, drip protection, desiccant type/capacity/location if justifiedCalculation, product data and installation record
Loading and sealStow pattern, separation, securing, closure, seal number and exception authorityPhotos, count, timestamp, seal and handover record
Arrival decisionWho attends opening, what is checked first, evidence sequence, hold/release and claim noticeSeal, door, roof, package and product-condition record

A nine-step prevention method

  1. Define the lot and intended chain. Link the exact tea lot, pack construction and shipment to the control sheet. A retail pouch inside a carton and a 50 kg lined sack do not have the same exposed materials or failure paths.
  2. Measure the product with an agreed method. State the sampling plan, analytical method, units, basis, limit and decision rule. Use the site's moisture-result guide and representative sampling method. One compliant composite does not prove every package is dry or sealed.
  3. Map the route rather than naming only the ports. Record likely dwell, transshipment, season, rail or sea legs and destination warehouse conditions. The purpose is to identify large temperature swings and long exposure periods, not to promise a weather forecast.
  4. Approve the finished package. Confirm liner identity, closure method, outer-pack strength and pallet/dunnage materials for the real contact time and route. Food-contact approval and water-vapour barrier performance answer different questions; use the packaging specification guide for the material and change-control fields.
  5. Inspect the empty container before loading. Check identity, cleanliness, dryness, odour, previous-cargo information where required, roof and wall condition, door seals, floor, vents and visible holes or contamination. Reject or obtain written approval for exceptions before tea enters the unit.
  6. Keep the loading operation dry. Do not load in rain or introduce wet pallets, timber, mats or cartons. Protect staged goods from wet ground and weather. Record any interruption and re-inspect affected materials.
  7. Engineer moisture control. Decide whether dry dunnage, package barrier, roof/side protection, container lining, desiccant or another measure is justified. If desiccant is used, calculate absorption capacity from the defined system and supplier performance conditions, then specify safe placement and prevention of direct contact or leakage. Desiccant is not permission to load wet cargo.
  8. Load, secure and document. Keep packages away from known drip or abrasion paths where the plan requires it, maintain the approved stow, and do not block container features contrary to the equipment or carrier instructions. Photograph key stages, package marks, protection, final doors and seal.
  9. Control arrival opening. Verify seal and exterior first; then record door area, odour, visible condensation, roof/walls, wet cartons or sacks and affected positions before unloading changes the scene. Segregate suspect goods and follow the prewritten hold, sampling, notification and claim process.

What desiccants and data loggers can and cannot prove

ToolUseful evidenceWhat it does not prove alone
Container desiccantAdditional vapour-absorption capacity under its specified operating conditionsThat cargo, pallets or container were dry; that the capacity was sufficient; or that packages stayed sealed
Temperature/RH loggerConditions at its location and sampling intervalSurface temperature, dew point at every wall, moisture inside every pack or cause of a wetting event
Moisture resultResult for the sample, method, date and lot link reportedContainer integrity, packaging barrier performance or distribution across every bag
Loading photographsVisible condition, stow and controls at recorded momentsHidden defects or conditions throughout the whole route

Codex CXC 1-1969, revised in 2022, says food should be protected during transport and that conveyances should maintain humidity, atmosphere and other conditions where necessary to prevent deterioration. Codex CXC 47-2001 adds controls for the transport unit, loading, in-transit storage and unloading of bulk and semi-packed food. These are hygiene references; the buyer still needs product-, route- and contract-specific controls.

Common buyer mistakes

  • Specifying a fixed number of desiccant units without capacity, route, cargo, pack or performance conditions.
  • Accepting "dry container" with no inspection fields, photographs, exception rule or named approver.
  • Checking tea moisture but ignoring wet pallets, cartons, timber and humid loading conditions.
  • Assuming a high-barrier liner compensates for poor seals, punctures or an unapproved material change.
  • Using plastic sheeting without considering where water will collect or whether total trapped moisture is excessive.
  • Blocking vents automatically, or relying on vents automatically, without container, carrier and cargo justification.
  • Treating one logger as a map of every package and container surface.
  • Opening, unloading and discarding wet packaging before recording the seal, container and damage pattern.
  • Confusing a voluntary transport code with destination law or a binding sales-contract promise.

Practical conclusion

The defensible sequence is identify the lot and pack - map the route - set product and material moisture controls - inspect the CTU - load only in dry conditions - calculate protective capacity - record stow and seal - preserve arrival evidence - apply the prewritten release or hold rule. It gives the buyer a traceable prevention and claims file instead of a desiccant count with no engineering basis.

Add the approved fields to the bulk green tea purchase specification, align loading evidence with Yunjing Tea's packing and container-loading options and quality-control checkpoints, then send the tea, pack, route and destination for a product-specific discussion.

Sources checked 24 August 2026: UNECE's official CTU Code page and the 2014 IMO/ILO/UNECE CTU Code; IMO's current-publications list dated 22 June 2026; UNECE's 2025 revision working document for WP.24's 69th session; Codex CXC 1-1969, revised 2022 and CXC 47-2001; ISO 11287:2011, confirmed current in 2021; and ISO 2233:2000, confirmed current in 2022.