How to Use Dunnage Bags for Safer Freight

A load can be correctly palletised and still arrive damaged if it has room to move. Gaps between pallets, crates or drums allow freight to shift under braking, cornering, vibration and rail impact. Knowing how to use dunnage bags correctly helps fill those voids, limit movement and protect product through the transport cycle.

Dunnage bags are not a substitute for proper load planning, blocking, bracing or restraint. They are a cargo-stabilising tool used in the right location, with the right bag type and inflation pressure. For warehouse teams, exporters and freight operators, the value is straightforward: fewer damaged consignments, less rework at receival and better use of available load space.

What dunnage bags do in a freight load

A dunnage bag is an inflatable bag placed in a void between freight units. Once inflated, it applies even pressure across the facing load surfaces, helping prevent side-to-side movement. They are commonly used in shipping containers, road trailers, rail wagons and intermodal loads.

The bag works best when freight is stable vertically and the void is consistent from the floor up. A bag placed between two uneven pallet stacks may fill the gap, but it cannot correct poor pallet construction, leaning product or unsecured freight. The contact surfaces need to be capable of accepting pressure without crushing, puncturing or sliding.

In practical terms, dunnage bags are suited to palletised cartons, boxed goods, timber packs, drums, bagged product and other freight where a clear void remains after the load is positioned. They are particularly useful where the load does not fully fill the width or length of a container or trailer.

How to use dunnage bags correctly

Start by loading the heaviest and most stable freight first. Keep pallets square, aligned and as close together as practical. The aim is to minimise open space before dunnage bags are introduced. A dunnage bag should fill a manageable void, not bridge an excessive gap created by poor loading.

Before placing the bag, inspect the area for exposed nails, broken pallet boards, sharp carton edges, metal strapping or damaged packaging. These can puncture the bag during inflation or while the load is in transit. Where needed, use protective boards or other suitable barrier material to create a smooth contact face. Do not place a bag directly against sharp or abrasive freight.

Position the deflated bag upright in the void, with the valve accessible for inflation and later deflation. The bag should sit centrally between the load faces rather than being folded, twisted or trapped under a pallet. Its height and width should provide broad contact with the freight. A small bag in a large, irregular void concentrates force in one area and is less effective.

Inflate the bag using a compatible inflation tool and regulated air supply. Follow the manufacturer’s stated pressure requirements for the bag grade and application. Pressure matters: underinflation leaves room for movement, while overinflation can damage cartons, deform product, split packaging or cause the bag to fail.

Inflate gradually and watch the load as the bag expands. Stop if pallets begin to lift, cartons bow excessively or the bag is being forced against an uneven surface. The objective is firm contact that removes lateral play, not maximum pressure. Once inflated, close and check the valve in accordance with the bag’s instructions.

For container loads, complete this process before the final doors are closed. Make sure the bag does not protrude into the door path or create a risk when doors are opened at destination. A restrained load should remain stable even if a bag loses pressure, so consider how the final row will be safely contained during unloading.

Match the bag to the void and transport task

Dunnage bags are available in different sizes, materials and strength ratings. The correct selection depends on the gap dimensions, freight weight, load surface and transport mode. Paper, polypropylene and woven outer constructions are used across different freight conditions, while inner liners provide the air seal.

Measure the void after the load has been positioned. A bag should be sized to fill the space without needing excessive inflation. If the void is very wide, consider changing the loading pattern, adding suitable void fillers or using engineered blocking and bracing. Trying to make one bag span a large gap can result in poor contact and a higher risk of movement.

The strength rating must also suit the expected forces. A light bag may be appropriate for modest pallet loads in a controlled road freight application. Heavier freight, longer distances, rail movements or export containers may require a higher-rated bag and a more comprehensive cargo restraint plan. The transport environment matters as much as the product weight.

Consider the surface of the freight as well. Smooth, rigid pallet loads provide a better bearing face than soft sacks, irregular machinery or loose cartons. If the load is compressible, inflation pressure may need to be lower, and additional restraint methods may be necessary to control movement.

Check the load before dispatch

A final inspection is worth the few minutes it takes. Check that the bag is centred, fully supported and not rubbing against a sharp edge. Confirm the valve is closed and accessible only if required. Look for unstable pallets, unsupported upper cartons and empty spaces elsewhere in the load.

Dunnage bags should be part of a wider load-securing process. Depending on the freight and carrier requirements, that may also include pallet wrap, strapping, load bars, blocking, timber bracing, friction mats or lashing. The appropriate combination depends on the product, vehicle, route and applicable cargo restraint obligations.

Do not rely on a dunnage bag to retain a load against container doors. Door-end restraint needs specific consideration because pressure can be released suddenly when doors are opened. Freight teams at the receiving end should be aware that a bag may be present and should open doors cautiously, particularly where the load has settled or shifted during transit.

Common mistakes that lead to freight damage

The most common issue is using a bag to solve a loading problem that should have been addressed earlier. Large voids, uneven stacks and poorly wrapped pallets create conditions a dunnage bag cannot reliably fix. Better pallet configuration and tighter load placement usually improve results before any bag is inflated.

Another frequent error is overinflation. More air does not mean better restraint. Excess pressure can transfer force into cartons or drums, damage packaging and reduce the bag’s service life. Use the recommended operating pressure and inspect the load while inflating.

Punctures are also preventable. Damaged pallets, protruding staples and sharp strapping should be identified before loading. A protective sheet or board can be useful where contact surfaces are rough, but it must be stable and suitable for the load. Loose materials inserted without thought can create a new movement risk.

Finally, avoid assuming every bag is reusable. Reuse depends on the bag construction, condition, previous use and the manufacturer’s guidance. Any bag showing abrasion, valve damage, contamination or loss of integrity should be removed from service.

Build dunnage bags into your load plan

The most reliable results come from planning void control before loading starts. Review pallet dimensions, container or trailer width, stack pattern and expected gaps. This lets the team allocate the correct bag size and any additional restraint materials before freight reaches the dispatch area.

For regular lanes and repeat products, record the loading configuration that works. A documented pattern improves consistency between shifts, sites and third-party carriers. It also makes procurement easier because bag sizes and quantities can be planned against expected freight volumes.

MH Direct supplies dunnage bags for commercial cargo protection applications, with practical options for businesses managing container, road and warehouse freight. For higher-value, unusual or heavy consignments, assess the full restraint method before dispatch rather than treating the bag as a last-minute fix.

Used with sound palletisation and suitable restraint, dunnage bags are a simple way to control the space that causes many freight damage claims. The key is not to inflate harder, but to load smarter, select correctly and inspect every consignment before it leaves site.