In short: a dunnage bag is an inflatable air bag placed in the empty voids between cargo inside shipping containers, truck trailers or rail wagons. The uninflated bag is slipped into the gap, inflated in seconds with an air compressor, and the void becomes a solid, cushioned brace — so cargo cannot shift, topple or collide during transport. Dunnage bags come in kraft-paper composite, PP woven fabric and large-valve series, sized roughly 50×100 cm to 120×180 cm, covering voids from about 10 to 50 cm.
Why Does Cargo Need Dunnage at All?
No matter how carefully you load, voids remain — between pallets, between cartons and the container wall, at the door end. Every brake, corner, rail shunt and ocean wave turns those voids into room for cargo to move. The traditional answers were timber frames, foam blocks and waste cardboard: slow to install, expensive to customize, and — in timber's case — subject to fumigation and quarantine paperwork on export. The dunnage bag replaces all of that with one tool: fill the void with air, and let pressure do the bracing.
How a Dunnage Bag Works
A dunnage bag has three parts, each doing one job:
- Outer bag — kraft paper composite or PP woven fabric. This is the strength layer; it resists abrasion against cargo and carries the load.
- Inner bag — an airtight PE or PA film that holds the compressed air.
- Valve — the one-way inflation valve (standard or large-bore) you connect the air gun to; it seals automatically once the gun is removed.
The bag arrives flat. You place it uninflated in the void, inflate it until it fits snugly between the cargo surfaces, and it becomes a pressure brace customized to that exact gap. Read our structure breakdown for the details on each component.
The Three Main Types
- Kraft paper dunnage bags — multi-layer kraft composite outer, strong abrasion resistance, recyclable; the workhorse for ocean container securing.
- PP woven dunnage bags — polypropylene woven outer, lighter and lower-cost, moisture-tolerant and reusable; popular for repeated road and rail use.
- Large-valve dunnage bags — a bigger one-way valve that inflates several times faster and seals instantly; built for loading docks securing many containers a day.
Still deciding between materials? See Kraft Paper vs. PP Woven Dunnage Bags: How to Choose.
Where Are Dunnage Bags Used?
Practically anywhere cargo moves in bulk: 20ft and 40ft sea containers, truck trailers, rail wagons and intermodal transport. Industries that rely on them include furniture and building materials, auto parts, home appliances, palletized cartons, paper rolls, bagged goods and drums — in short, any shipment where pallets or cartons don't fill the container wall to wall.
What to Know Before Ordering
Three practical points to get right up front:
- Size follows the void. Measure the void width after loading, then match a bag size to it — never size from the container dimensions alone. Our size chart maps common bag dimensions to void ranges.
- Order terms. Tezheng's export MOQ is 5,000 pcs for dunnage bags, with a lead time of about 20 days from production to port. Order samples first and trial them in one real container with your actual cargo.
- Testing. Tezheng's dunnage bags have passed SGS chemical safety testing (TPCH). This is a chemical safety test — it is not railroad performance certification.
Frequently Asked Questions
What is a dunnage bag used for?
A dunnage bag fills the empty voids between cargo inside shipping containers, truck trailers and rail wagons. Once inflated, it braces cargo against the container walls, preventing shifting, toppling and collision damage during braking, cornering, rail shunting and the rolling of ocean vessels.
Is a dunnage bag the same as an air pillow used in packaging?
No. Packaging air pillows cushion individual products inside a box; dunnage bags are multi-layer, pressure-rated cargo braces built to hold tons of freight. A dunnage bag has a tough outer bag, an airtight inner film and an inflation valve — it is a cargo-securing tool, not packing filler.
Can dunnage bags be reused?
PP woven dunnage bags are designed to be reusable when kept at correct pressure and handled carefully. Kraft paper dunnage bags offer limited reuse depending on pressure and cargo contact. Always inspect a used bag for punctures or valve damage before reinflation.
Are dunnage bags accepted for international shipping?
Yes. Unlike timber bracing, dunnage bags need no fumigation or quarantine paperwork, which speeds up export clearance. Tezheng's dunnage bags have passed SGS chemical safety testing (TPCH). Note this is a chemical safety test, not railroad performance certification.
What is the minimum order quantity and lead time for dunnage bags?
Tezheng's export MOQ is 5,000 pcs for dunnage bags, with a lead time of about 20 days from production to port. We recommend ordering samples first and trialing them in one real container before placing a bulk order.
Related reading: learn how to use a dunnage bag in a container step by step, and check safe inflation pressure before your first installation.