Mục lục
Reviewed and updated by ICD - Week 24/2026
Quick summary:
- Choosing the right dunnage bag follows four steps: set the load level (AAR), pick the material (kraft or woven PP), calculate the size (width and height), and check valve compatibility.
- Raise the AAR level at least one step for sea or rail transport - dynamic force can be 2-3x the static load.
- Bag width should be about 2-3x the void width; bag height should cover at least 2/3 of the load height.
- Prioritize a fast valve (20 mm+) with auto-lock for speed and a secure seal.
How to choose a dunnage bag in 4 steps
Choosing the right dunnage bag is the first step to securing cargo safely in container transport. This guide walks through four practical steps. For the underlying mechanics, see what a dunnage bag is.
Step 1: Set the load level (AAR)
This is the most important step. The bag’s level follows the AAR standard and must match the cargo weight and transport mode.
- Level 1 (light to medium): total container weight under 20 tonnes, usually road transport or tightly palletized goods.
- Level 2 (heavy, intercontinental): over 20 tonnes, especially ocean or rail with large impulse.
- Level 3 (very heavy, high impact): heavy goods such as large paper rolls and industrial machinery, or routes with strong vibration.
Always raise the level by at least one step for sea or intercontinental rail. Dynamic (shunting) force can be 2-3 times the static load, so choosing a level below the expected impact leads to ineffective bracing and serious damage. See the technical metrics guide for how AAR levels are rated.
Step 2: Choose the material - kraft or woven PP?
After the level, decide between the two common outer-shell materials. The inner bladder is always a PA/PE composite for tensile strength and air retention.
Kraft paper bag
A multi-ply virgin kraft shell with good friction that biodegrades easily. Low cost, light, easy to dispose of, suited to light-to-medium loads (Level 1-2) such as cartons, consumer goods and lighter bottled chemicals - the cost-optimal choice for one-way shipments. Not suited to prolonged damp or reuse. For high-value cargo or humid tropical routes, ensure the kraft is PE-coated for moisture resistance.
Woven PP bag
A cross-woven polypropylene shell that is extremely tough and tear-resistant. It handles very heavy loads (Level 3+), resists water well, and far outperforms kraft on puncture resistance - and it is reusable. Required for machinery, steel coils, building materials, or closed-loop supply chains shipping back and forth. For sharp-edged goods or more than 3 reuses, invest in woven PP: the higher upfront cost is offset by tear resistance and reuse life. See what kraft paper is for shell detail.
Step 3: Calculate the bag size (width and height)
Width
The bag width must exceed the gap by at least about 5 cm so it can expand fully and press evenly. ICD’s rule of thumb: bag width should be about 2-3 times the gap width for ideal fullness. For a 20 cm gap, choose a 40 cm bag (small gap) or 60 cm (large gap or high-load need). Do not use an over-wide bag in a narrow gap - it inflates unevenly into a sphere, reducing contact area and effectiveness.
Height
The bag height must cover at least 2/3 of the load height to spread force evenly. In a container (standard 240 cm high) with goods stacked 200 cm, choose a bag 120-180 cm tall. A taller bag locks both the body and upper layers, stopping the load tipping or sliding over the bag when the container sways.
Step 4: Check valve and gun compatibility
Performance depends on inflation speed and the valve’s seal. Prioritize a fast valve with a large diameter (20 mm or more) and an auto-lock, which cuts inflation time to about one third of an old-style valve. Use a dedicated gun with a built-in pressure gauge so you reach the correct pressure - avoiding under-inflation (weak force) or over-inflation (burst risk).
Frequently Asked Questions (FAQ)
What AAR level for ocean freight?
Level 2 is the usual minimum; raise to Level 3+ for very heavy goods or rail. Always step up at least one level for sea or intercontinental routes.
How wide should the bag be relative to the gap?
About 2-3 times the gap width, and at least 5 cm wider, so it inflates fully and presses evenly.
How tall should the bag be?
At least 2/3 of the load height, so it locks both the body and upper layers against sway.
When is woven PP worth the extra cost?
For sharp-edged or very heavy goods, humid routes, or more than 3 reuses - the tear resistance and reuse life lower total logistics cost.
Contact ICD Viet Nam
For help choosing the right dunnage bag for your cargo, contact our team for specifications and a quote.
- Northern Vietnam: 0983 797 186 / 090 345 9186 / 090 5859 186
- Southern Vietnam: 098 6784 186
- Email: sales@icdvietnam.com.vn
- Zalo: Chat on Zalo
