Shipping managers know that a stable load is cheaper than a freight claim, and that lateral movement in rail, truckload, and intermodal lanes often starts small, a few inches of drift that becomes broken stretch wrap, crushed corners, and toppled pallets. Dunnage air bags solve for that side-to-side creep when used with edge protectors, corrugated void fillers, and strapping, but the details matter, correct material choice, correct load rating, correct valve and inflator, correct PSI, correct placement between pallets.
This guide explains what dunnage bags are, how they are built, how to size and place them, and how to inflate them safely and repeatably. It also includes a pre-load trailer checklist and best practices for mixed-height pallets. The intent is practical, to reduce damage and downtime and to support safer, more repeatable unitization across modes.
Breckenridge Paper & Packaging supports these programs with materials, equipment, and specification guidance, integrating dunnage bags with edge protection, blocking and bracing, and strapping selections, and providing consultative reviews to simplify decisions and control total landed cost.
What a dunnage air bag is and where it fits
A dunnage air bag is an inflatable bladder used to fill lateral voids between pallets, between pallets and trailer walls, or between stacked units to prevent shifting under acceleration, braking, cornering, vibration, and rail humping. The bag exerts outward pressure to create friction and resist movement, it is not a vertical load-bearing device and should not be used to support top load or bridge weight.
Dunnage bags complement, not replace, other securement components. Edge protectors transfer strap tension without crushing carton edges, corrugated void fillers or honeycomb panels span larger cavities or stack height mismatches, and strapping or banding holds each palletized unit tight. In practice, a stable load uses several elements working together, unitized pallets with stretch wrap, horizontal or vertical strapping as needed, edge protection on vulnerable corners, then dunnage bags in the lateral gaps to lock the pattern.
For additional protective solutions that round out the kit, many teams source edge protection and cushioning as part of a single program, see Breckenridge’s protective packaging overview for edge protector and related options that integrate with trailer bracing.
Construction types, valves, and load ratings
Two primary constructions are common:
- Kraft paper, multiple plies of Kraft paper with a polyethylene inner bladder. These are cost-effective, widely used for over-the-road truckload and many intermodal lanes, available in light to heavy-duty ratings. The paper shell provides abrasion resistance against pallets and walls.
- Polywoven or polylaminate, a woven polypropylene or laminated outer with a polyethylene bladder. Higher puncture resistance and moisture tolerance, favored for rail and export containers, repeat use in controlled operations, and heavier lateral loads.
Valve types influence speed and repeatability. A quick-fill push-pull or screw-in valve with a matched dunnage bag inflator allows fast, metered fill and simple deflation for removal. Legacy duckbill styles exist but are slower and less consistent. Standardize on one valve family per site to simplify tools and training.
Load ratings are typically published as Level 1 through Level 5, or as maximum void width and working pressure guidance. The rating is about lateral restraint capacity, not vertical stacking. Select a level based on mode, gap size, and cargo mass, for example:
- Truckload, light to moderate gaps and balanced weights, Level 1 to Level 2.
- Intermodal or mixed lanes with higher impact profiles, Level 2 to Level 4.
- Rail with larger voids or heavier mass, Level 4 to Level 5 and polywoven shells.
Always match bag size to the void. A bag should span at least two-thirds of the pallet height it is stabilizing and contact broad, flat surfaces, not sharp edges.
Placement fundamentals to prevent lateral movement
Place bags between stable, wrapped pallets or between a pallet and a flat, strong surface like a trailer wall or corrugated void filler. Avoid placing a bag against protrusions, strapping buckles, open board ends, or nail heads. Center the bag vertically so pressure distributes across the strongest carton panels; when load heights differ, align the center of the bag with the center mass of the taller unit and add a corrugated pad or honeycomb to bridge the short side.
For patterns, common placements include one centered bag for short voids under 12 inches, two vertically stacked bags for tall loads or voids greater than 18 inches, and paired bags along a longer tunnel when bracing multiple pallets in a row. Keep at least 4 inches of lateral clearance before inflation so the bag can seat and pressurize properly.
Step-by-step inflation guide
Required tools include a compatible dunnage bag inflator, a compressed air source with a regulator, and a calibrated pressure gauge. A simple, consistent routine reduces overfill risk and improves repeatability across shifts.
- Inspect the bag, confirm correct size, construction, and valve, check for cuts, abrasion, or seam defects, verify the bladder is intact.
- Prep the void, remove nails or splinters, add a corrugated sheet where surfaces are uneven, confirm the gap width is within the bag’s rated range.
- Position the bag flat, centered in the void, with the valve accessible at the aisle side when possible for easy removal.
- Connect the inflator, seat the nozzle fully on the valve, and confirm the regulator is set to the target.
- Inflate to working pressure, most truckload applications run 2 to 6 PSI depending on bag level, void size, and product rigidity; rail often requires higher within the manufacturer’s limits, do not exceed the printed maximum PSI on the bag or the inflator’s setting.
- Check seating, confirm full face contact on both sides, no pinches or sharp contact points, listen for leaks, tap the surfaces to ensure firm resistance without bulging cartons.
- Secure the valve, disconnect the inflator, recheck pressure after a minute, and note the bag location and PSI on the load sheet for traceability.
- Before closing, perform a light push test on the adjacent pallets, verify minimal movement, and add a second bag or bridging panel if drift is observed.
Avoid overfilling. An over-pressurized bag can crush cartons or deform stretch wrap. Underfill leaves slack that will work loose in transit. A regulated inflator and a simple checklist create consistency.
If you are setting up tools, Breckenridge can supply a matched dunnage bag inflator and provide training on regulator settings and valve compatibility as part of a specification review.
Trailer inspection checklist before loading
- Floor and walls, free of protruding nails, screws, or broken boards, dry and clean.
- E-tracks and anchor points, secure and undamaged if used for supplemental bracing.
- Doors and seals, close smoothly, no daylight at edges, gaskets intact.
- Interior dimensions, confirm planned pattern fits, note any crown in the floor or bow in the walls that changes gap sizes.
- Weight distribution, plan axle balance and even left-right mass to reduce sway.
- Environmental considerations, if moisture is likely, favor polywoven bags and add liners or overwraps where appropriate.
This is a quick check that prevents punctures and surprises that compromise bracing, and it pairs well with unit-level checks for stretch wrap containment force and strap tension.
Best practices for mixed-height pallets
Mixed heights are common in retail and parts distribution. The goal is to present flat, broad surfaces to the bag and to transfer pressure into strong edges and panels. Bridge height differences with corrugated sheets or honeycomb panels on the shorter side so the bag bears evenly. Use edge protectors on the taller unit to spread load from any adjacent strapping and to prevent corner crush. If the difference is significant, run two smaller bags vertically rather than one oversized bag that will bow. Keep heaviest pallets on the floor, avoid stacking unstable tops, and consider adding cross-tying straps on the tall units for additional containment.
For supporting materials, see options for kraft paper and corrugated sheets that help create flat faces and distribute pressure around corners without abrasion.
How strapping, edge protection, and dunnage work together
Strapping secures each pallet as a single unit, adding vertical and horizontal containment that stretch wrap alone may not provide. Steel banding or high-strength polyester strap can clamp loads with consistent tension, while edge protectors prevent the strap from biting into carton edges. Dunnage bags then address the system-level gap between units inside the trailer or container. The result is unit-level integrity plus trailer-level stability.
Breckenridge supplies strapping for shipping, including steel banding options, as well as edge protector formats under a broader protective packaging portfolio, enabling one specification to cover unitization and in-transit bracing.
FAQs
- What is a dunnage air bag?
- An inflatable device placed in lateral voids between pallets or between cargo and walls to prevent side-to-side movement during transport. It provides friction and restraint, it is not intended to hold vertical loads.
- How do you fill a dunnage bag?
- Use a matched dunnage bag inflator and a regulated air source, seat the nozzle on the valve, inflate to the manufacturer’s working pressure range for the mode, typically 2 to 6 PSI for many truckload cases, then verify full face contact and secure the valve, never exceed the printed maximum PSI.
- Why is it called dunnage?
- Dunnage is an old shipping term for materials used to protect and secure cargo by filling spaces, blocking, and bracing. Air bags are one form of dunnage used to stabilize loads in transit.
- How long do air bags stay inflated?
- Quality bags with intact valves and proper seating typically hold working pressure for the duration of a standard trip in truckload or intermodal service. Time in transit, temperature swings, and surface abrasion can affect retention, so pre-trip checks and correct PSI help maintain performance.
- What is the purpose of strapping?
- Strapping binds cartons and components into a tight unit, resists vertical and horizontal separation, and maintains containment during handling and vibration, it complements stretch wrap and enables dunnage bags to work against a solid face.
Next steps and support
Breckenridge brings a customer-first mentality, helping teams choose the right bag construction and level, match valves and inflators, and integrate edge protection, corrugated void fillers, and strapping into a consistent load plan that reduces freight claims. Contact Breckenridge for bag sizing help and bulk pricing, and request a free lane assessment to map lane hazards and reduce damage trends. For related materials and consultation support, review our protective packaging options, explore strapping selections including steel banding for heavy-duty needs, and connect with our team through packaging consulting to align materials, equipment, and specifications with your lanes and goals.
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