Dunnage is material placed in and around cargo to protect it, separate it, and support proper stowage — traditionally wood, though modern shipping increasingly uses plastic, matting, and inflatable airbags as well.
What Dunnage Actually Does
- Protects cargo from contact damage — cushioning between cargo units and against the ship’s structure
- Separates incompatible cargoes — preventing cargo types that could contaminate or react with each other from direct contact
- Prevents moisture damage — raising cargo off a hold’s steel deck (which can sweat with condensation) and improving air circulation beneath cargo
- Distributes weight — spreading concentrated point loads across a wider area of the deck or tank top, particularly important for heavy or unevenly-shaped cargo
- Improves ventilation — creating air gaps that allow moisture and heat to dissipate rather than accumulate around cargo
Wood Dunnage and Pest Regulations (ISPM 15)
Wood packaging material, including wood dunnage, used in international trade is subject to ISPM 15 (International Standards for Phytosanitary Measures No. 15) — requiring heat treatment or fumigation of the wood and a specific stamp/mark certifying compliance, to prevent the international spread of wood-boring pests and diseases. Non-compliant wood dunnage can be rejected by customs authorities at destination, causing real delays and costs.
Modern Alternatives to Wood Dunnage
Given ISPM 15 compliance requirements and cost, many operations now use plastic dunnage, synthetic matting, or inflatable dunnage airbags (which fill void spaces between cargo units and can be deflated and reused) — genuinely practical alternatives that avoid the wood-specific regulatory requirements entirely.
Dunnage in Practice
Proper dunnage placement is part of a competent stowage plan, not an afterthought — inadequate dunnage is a real, documented cause of cargo damage claims, particularly for cargo susceptible to moisture (paper products, certain foodstuffs) or requiring separation from other cargo types.
Exam Relevance
Dunnage’s functions, ISPM 15 wood packaging requirements, and its role in proper stowage planning are core Cargo Work topics in deck officer competency exams.