Pneumatic Dunnage Air Bags: How to Choose the Right Bag (PSI, Gap Size, and Placement)

Unsecured loads shift.

Shifted loads damage freight.

And damaged freight costs money.

Avoid that problem altogether by selecting the correct pneumatic dunnage air bag for your load. Pneumatic dunnage air bags are one of the most efficient tools available for filling void gaps, stabilizing pallets, and preventing load movement in transit. However, the right bag for one shipment may be the wrong bag for another. This guide covers the practical decisions that matter most: how to size a bag for your void gap, what PSI means in real terms, which material fits your application, and how placement and shipping modality change the equation.

Quick Answer: How to Choose the Right Dunnage Air Bag

Not sure where to start? Use this three-step framework:

1. Measure the void gap. The gap between your load and the container or trailer wall determines the bag size you need. Width, height, and depth all matter.
2. Choose the right material level. Paper dunnage bags are effective for dry, controlled environments. Polywoven bags handle rougher handling, moisture exposure, and heavier loads.
3. Match your modality and load weight. Over-the-road, intermodal, boxcar, and ocean freight each present different force profiles. The bag that works in a domestic OTR trailer may not be rated for an intermodal container crossing state lines.

If you can answer those three questions, you can narrow down the right bag quickly. If any of those variables are uncertain (unusual load geometry, mixed modalities, high-value freight) that’s when it’s worth talking to a packaging expert before you order.

What “PSI” Actually Means for Dunnage Air Bags

PSI (pounds per square inch) describes the air pressure inside an inflated dunnage bag. For most standard dunnage air bags, the recommended working pressure falls in the range of 2 to 3 PSI, which may seem low, but across a large bag surface area, that translates to significant lateral force against your load.

Why over-inflation is a problem:

More pressure does not mean more protection. Inflating beyond a bag’s rated PSI creates several risks:

• The bag becomes rigid and loses its ability to absorb vibration and shock
• Excess pressure can cause burst failure, particularly if the bag contacts a sharp edge or uneven surface
• Over-inflated bags can exert force on the load itself, potentially damaging the product or packaging

Always follow the manufacturer’s rated working pressure for the specific bag you’re using. If you’re unsure of the correct PSI for your application, default to the lower end of the recommended range and verify with your supplier. A pressure gauge or regulated inflator, not a compressed air line opened freehand, is the right tool for this job.

Measure the Void Gap Correctly

The void gap is the empty space between your load and the wall, door, or adjacent unit. Getting this measurement right is the foundation of proper bag selection.

How to measure:

• Width: The horizontal distance across the open void
• Height: The vertical span of the void (the bag should cover as much of this as practical)
• Depth: How far the void extends into the load face (relevant for determining how much surface contact the bag will achieve)

Common measurement mistakes to avoid:

• Measuring at only one point when the void is uneven (measure at the widest point)
• Ignoring vertical height and ordering a bag too short to provide adequate coverage
• Assuming partial contact is acceptable (bags work best when they make full, flush contact with both load faces)
• Forgetting to account for pallet overhang or irregular load geometry

If the void is inconsistent or the load face is uneven, a single bag may not be sufficient. In those cases, using approved dunnage materials to create a more consistent void may be more appropriate.

Gap Size Guidance Table

The table below provides general sizing guidance based on void width. These are starting-point recommendations. Actual selection should account for load weight, height, and modality.

This table provides general guidance only. Gap size is one variable among several; load weight, modality, and contact surface all affect proper bag selection. Void spaces can be reduced by utilizing appropriate dunnage materials in conjunction with the air bags. If you’re unsure which bag will work best for your situation, talk to our packaging experts before placing an order.

Paper vs. Polywoven: Which Dunnage Bag Material Fits Your Shipment?

The two primary materials for dunnage air bags are kraft paper (typically multi-ply) and polywoven (woven polypropylene). Each has a distinct application profile.

Paper dunnage bags are well-suited for:

• Dry, climate-controlled environments
• Domestic over-the-road shipments with predictable handling
• Applications with moderate load weights
• Single-use or low-reuse scenarios

Polywoven dunnage bags are the better choice when:

• Moisture exposure is a factor (damp warehouses, outdoor loading, ocean freight)
• Handling is rough or the bag may contact abrasive surfaces
• The application involves heavier loads or higher-vibration environments
• Extended or intermodal transit increases wear risk

Polywoven bags generally carry higher pressure ratings and offer better puncture resistance than paper equivalents. Polywoven bags are less expensive per unit, offer a higher quantity per pallet, require less space, and offer enhanced durability.

When in doubt, consider the worst-case handling scenario for that shipment, not the average one.

Placement Basics: Where Dunnage Air Bags Work Best

Correct placement is as important as correct sizing. A properly rated bag placed incorrectly will underperform or fail entirely.

Core placement principles:

• Maximize surface contact. The bag should press flat against both load faces across as much area as possible. Partial contact concentrates force and increases burst risk.
• Avoid sharp edges and protrusions. Strapping, pallet corner boards, exposed fasteners, and rough timber can puncture or abrade the bag during inflation and transit. Use edge protection where contact is unavoidable.
• Stabilize before inflating. The load should be positioned and blocked before you begin inflation. Inflating a bag to move freight into position puts unnecessary stress on the bag and is a misuse of the product.
• Center vertically when possible. Placing the bag at mid-height on the load face distributes lateral force more evenly than placing it near the top or bottom.

Placement decisions also depend heavily on load geometry. Uniform pallet stacks behave differently from irregularly shaped freight or mixed-SKU loads. For complex load plans, a placement diagram specific to your configuration is worth the investment. Sunrise’s load securement solutions team can help with that.

Modality Tips: Boxcar vs. Intermodal vs. OTR vs. Ocean

Shipping modality affects the forces your load will experience, which directly affects the dunnage bag requirements. What works in one environment may be undersized or inappropriate in another. Use the guide below to determine which option would be best for your load, or contact our experts and we’ll help you select the right fit.

Boxcar (Rail) Railcar shipments are subject to significant longitudinal shock forces (slack action during coupling and braking can create sudden, high-impact loads.) Dunnage bags used in boxcars typically need to be rated for higher forces than OTR equivalents. Polywoven bags are often preferred. Always verify that the bag is AAR approved for rail use.

Intermodal Intermodal containers move through multiple handling environments (truck, rail, and ocean) in a single journey. This means cumulative wear, variable force directions, and exposure to moisture. Polywoven bags with higher pressure ratings are the standard choice for intermodal. See Sunrise’s shipping modalities hub for more detail.

Over-the-Road (OTR) OTR is the most common application for dunnage air bags and offers the broadest range of suitable bag types. Road vibration and lateral forces during cornering are the primary concerns. Both paper and polywoven bags are used in OTR, with material selection driven by load weight, moisture exposure, and reuse requirements.

Ocean Freight Ocean containers experience rolling, pitching, and stacking forces that exceed most domestic applications. High-humidity environments accelerate degradation of paper bags. Polywoven bags with high burst strength ratings are standard for ocean applications, and compliance with applicable regulations (including AAR and EUMOS standards, where relevant) should be confirmed before use.

Before You Inflate: A Quick Checklist

Run through this before pressurizing any dunnage air bag:

• Void gap measured at its widest point
• Bag size confirmed appropriate for gap width and height
• Load faces clear of sharp edges, protrusions, or exposed hardware
• Edge protection applied where needed
• Load is fully positioned and stable before inflation begins
• Regulated inflator or pressure gauge in use, not an unregulated air line
• Inflation performed to manufacturer’s rated PSI, not above it
• Bag surface fully in contact with both load faces once inflated
• Bag inspected for visible damage, wrinkles, or pinching before sealing the load

This checklist applies regardless of bag type or modality. Skipping any of these steps is where most in-service failures originate.

When to Call Sunrise for Help

Standard applications are straightforward. But many shipments aren’t standard. Mixed freight, unusual container dimensions, high-value loads, or multi-modal routing all introduce variables that generic bag selection guidance won’t cover.

Sunrise Manufacturing’s packaging experts work directly with shipping and logistics teams to develop load plans, select the right bag for specific applications, and identify placements that reduce damage risk. If you’re dealing with a gap size outside the normal range, a modality that demands compliance documentation, or a recurring damage issue you haven’t been able to solve with off-the-shelf products, that’s the conversation worth having.

Talk to our packaging experts or request guidance on selecting the right dunnage air bags for your void gap and modality.

Frequently Asked Questions

What are pneumatic airbags used for in shipping?

Pneumatic dunnage air bags are used to fill void gaps between freight and the walls, doors, or adjacent cargo inside a shipping container, railcar, or trailer. When inflated, they apply lateral pressure against the load to prevent shifting during transit. They’re used across over-the-road, intermodal, boxcar, and ocean freight applications.

How much PSI should I use for dunnage air bags?

Most standard dunnage air bags are designed to operate at 2 to 3 PSI. The correct working pressure depends on the specific bag’s rating. Always follow the manufacturer’s specification. Over-inflation reduces performance, increases burst risk, and can transfer damaging force to the load itself. Use a regulated inflator with a gauge rather than an uncontrolled air source.

How do I choose a dunnage bag size for my void gap?

Measure the void gap at its widest point and match that to the appropriate bag width range. Height coverage matters as well; the bag should span as much of the vertical void as practical. As a general rule: gaps up to 4 inches call for narrower bags (12–18 inches); gaps of 4–8 inches typically require 18–24 inch bags; larger gaps may need 24–36 inch bags or multiple bags. When in doubt, contact your supplier with the gap dimensions and load details.

Paper vs. polywoven dunnage bags: which is better?

Neither material is universally better. Selection depends on the application. Paper bags are cost-effective for dry, domestic OTR shipments with moderate loads. Polywoven bags are more durable, moisture-resistant, and better suited for rough handling, intermodal, and ocean freight. The right choice depends on your environment, load weight, and whether the bag will be reused.

How do I inflate dunnage air bags safely?

Use a regulated inflator with a pressure gauge. Insert the inflation valve fully before pressurizing. Inflate gradually to the rated working PSI, do not exceed the manufacturer’s maximum. Keep the bag clear of sharp edges during inflation. Never use an unregulated air line or attempt to inflate by hand. Once inflated, inspect the bag for visible bulging, pinching, or surface damage before closing the load.

What is the difference between intermodal and OTR dunnage bag requirements?

OTR (over-the-road) shipments typically experience road vibration and lateral force during turns. Intermodal shipments move through multiple environments and are subject to cumulative wear, variable forces, and moisture. Intermodal applications generally require higher-rated polywoven bags and may have specific compliance requirements. OTR allows more flexibility in bag material selection.

Can dunnage air bags be reused?

Polywoven dunnage bags used in rail shipments should not be re-used under any circumstance. Polywoven OTR bags are more suitable for possible reuse, provided they pass a visual inspection for damage, puncture, or valve wear before each use. Dunnage Paper bags are typically designed for single-use applications. Always inspect any bag before reuse and replace it if there is any doubt about its integrity.

Are neumatic air bags the same as pneumatic airbags?

Yes, “neumatic airbags” is a common misspelling of “pneumatic airbags.” Both terms refer to the same product: inflatable bags used to secure freight in shipping containers, trailers, and railcars by filling void gaps and preventing load shift.

What causes dunnage air bags to fail in transit?

The most common causes of in-transit failure are over-inflation, contact with sharp edges or protrusions, inadequate surface contact with load faces, and using a bag rated below the force requirements of the application. Proper sizing, correct placement, and inflating to the rated PSI can address the majority of these failure modes.

When should I contact a load securement specialist instead of selecting bags myself?

If your void gap is outside the standard range, your freight is high-value or fragile, your shipping route involves multiple modalities, or you’ve experienced repeated damage despite using dunnage bags, it’s worth consulting a specialist. Sunrise Manufacturing offers application guidance and load planning support. Request help here.