How to Inflate a Dunnage Bag: Step-by-Step Guide and Common Mistakes

Most in-transit cargo damage happens when the load shifts inside the container. The simplest way to stop that shift is a dunnage bag (also called a container air bag), but its effectiveness depends entirely on correct inflation. A poorly inflated bag either fails to secure the load or bursts before it ever does its job.

This guide answers exactly how to inflate a dunnage bag, step by step. You will also learn the right pressure levels and the mistakes crews make most often in the field. If this is your first time using one, it helps to first review what a container air bag is.

• How to prepare and measure voids before inflating
• The full step-by-step inflation procedure
• Correct PSI values by AAR level
• Five common mistakes and how to fix them

Table of Contents

• Before You Inflate: Proper Preparation
• How to Inflate a Dunnage Bag Step by Step
• Correct Pressure (PSI) Values
• Five Common Mistakes and Their Fixes
• Post-Inflation Checks and Deflation
• Frequently Asked Questions

Before You Inflate: Proper Preparation {#preparation}

A successful application starts before you pick up the gun. Once loading is complete, identify every void inside the container one by one. Assess the gaps between pallets, the space between the load and the container wall, and any top voids separately. Because each gap can differ in width, measure it with a tape rather than by eye for a reliable result.

After measuring the void, choose a bag that fits that dimension. Correct sizing is critical: the bag should cover the maximum surface of the load it braces without protruding above it.

According to the international CTU Code, a dunnage bag is not meant to “push cargo into place.” It is meant to stabilize a load that is already positioned correctly. In other words, it is a securement tool, not a positioning tool. This distinction is the foundation of every good application.

How to Inflate a Dunnage Bag Step by Step {#step-by-step}

Always inflate the bag inside the vehicle or container. Inflating it outside and then trying to insert it into the void is the wrong approach. Follow the steps below.

1. Position it: Place the deflated bag in the center of the void you measured. Align the edges of the bag with the edges of the neighboring pallets.

1. Center it: For best results, center the bag with roughly 15 cm of clearance from the top and 15 cm from the bottom between the pallets. Observe the position against the remaining gap.

1. Attach the gun: Fit the inflation gun, or the nozzle adapter on your standard air gun, firmly onto the bag’s valve. High-pressure air from the compressor passes through the valve and fills the bag.

1. Inflate gradually: Inflate in stages, not all at once. Adjust the fill level to the remaining void. Add air until the bag sits snugly between the two loads.

1. Check the pressure: Stop once the bag fully fills the void and braces the load toward the walls. Aim for a firm bag that still keeps some flex when you press it by hand.

This procedure applies to road, sea, rail, and air freight alike.

Correct Pressure (PSI) Values {#psi-values}

The right pressure determines both safety and performance. Most standard air bags operate at a low working pressure of around 2-3 PSI. The final value, however, depends on the bag’s level and the application.

Below are common working-pressure figures based on the AAR (Association of American Railroads) classification:

• Level 1: ~3 PSI working pressure — road and standard container loads.
• Level 2: ~4 PSI — rail and ocean-container shipments.
• Level 3: ~6 PSI — lengthwise bracing in rail transport.
• Level 4: ~8 PSI — heavy industrial loads and the heaviest rail freight.

Atlantik Dunnage Level 1 bags use a 65 gr + 25 gr laminated outer coating and withstand an 8 PSI impact pressure. Sized correctly, a single bag braces roughly 3-4 tons of load between pallets.

One rule stands above the rest: never approach the burst pressure. The UNECE CTU Code warns that cargo forces should never be allowed to reach the bag’s burst pressure, and that you should always keep a safety margin.

Five Common Mistakes and Their Fixes {#mistakes}

Most field failures come down to a handful of preventable errors. Here are the most frequent.

1. Over-inflation. This is the number-one mistake. Excess air raises burst risk and tears the bag if it meets a sharp edge. Fix: release excess air by cracking the valve open slightly.

2. Ignoring altitude and temperature. On mountain passes or in air freight, ambient pressure drops as altitude rises and the bag expands. A bag inflated fully at sea level can burst at higher elevations. Fix: keep the pressure slightly lower on routes with altitude change.

3. Under-inflation. A loose bag cannot fill the void, so the load moves. Fix: add air until the bag makes full contact with both surfaces.

4. Wrong bag size. A bag too small for the void cannot cover enough surface. Fix: measure the gap and select the right size, or reduce the void.

5. No edge protection. Metal corners and protrusions puncture the bag. Fix: place cardboard or foam protection at contact points.

Post-Inflation Checks and Deflation {#checks}

The job is not done the moment the bag is full. A quality bag should hold at least 90-95% of its pressure after 72 hours, in line with SGS air-tightness testing. If you see noticeable deflation in a short time, the bag likely has a puncture or a valve problem.

On long ocean voyages, inspect the bags visually again within the first few days. Temperature and humidity swings can affect pressure. If you notice slack, top it up with a few seconds of extra air to bring it back to the ideal level.

Deflating the bag at the destination is simple. Loosen the valve cap to release the air, then fold and store the bag. You can reuse polypropylene bags after checking for tears, punctures, or valve damage. This inspection habit improves both transport safety and cost efficiency.

Conclusion

A properly inflated dunnage bag delivers your cargo undamaged even on months-long voyages. In short: measure the void accurately, choose the right level, inflate gradually, stay well below burst pressure, and protect sharp edges. Accounting for altitude and temperature prevents most bursts before they ever happen.

If you want the right level and size of air bag for your loading operations, you can rely on Atlantik Dunnage’s products and application support. The right product paired with the right technique cuts your damage-claim costs directly.

Frequently Asked Questions {#faq}

How many PSI should I inflate a dunnage bag to?

Most standard bags operate at a low working pressure of 2-3 PSI. The exact value depends on the bag level, so always follow the manufacturer’s rated pressure and never approach burst pressure.

What tool do I use to inflate a dunnage bag?

You use an inflation gun, either a dedicated dunnage bag inflator or a standard air gun fitted with a special nozzle adapter connected to a compressor.

Are dunnage bags reusable?

Woven polypropylene bags can be reused after inspection if there are no punctures, tears, or valve damage. Most kraft paper bags are designed for single use.

Why do dunnage bags burst?

The most common cause is over-inflation. Altitude gain, rising temperatures, and contact with sharp edges also increase the risk of bursting.