Dunnage Air Bags 90 x 180: Practical Guide
Cargo that arrives still
The SECAL 90 × 180 cm dunnage air bag fills the void between your cargo and the container walls, applying constant lateral pressure that stops impacts, shifting and damage for the whole voyage. This guide shows you how to use it properly, step by step.
1. The problem: a container vibrates, brakes and rolls for weeks
Between load port and destination the cargo takes accelerations, braking, turns and the roll of the ship. Every centimetre of void is room for goods to move, strike each other and be damaged. The air bag removes that void.
It blocks movement
Inflated under pressure it acts as a flexible wall that holds the cargo firmly in place against braking, turns and sea swell.
It absorbs impact
It works as a giant cushion: when the transport takes a jolt, the bag takes the energy instead of the goods.
It stops the domino effect
It prevents an unstable stack from falling and bringing down or crushing the rest of the load.
A container can swing 20–30 °C in internal temperature as the ship crosses climate zones: the cargo expands, contracts and the void changes size during the voyage.
2. Anatomy of a SECAL bag
Inflation valve
On the edge, for easy access with the doors open. It opens and closes many times — the bag is reusable.
Woven polypropylene outer
High resistance to tearing and puncture. It does not harden or crack under constant movement and resists moisture.
Polyethylene inner bladder
The sealed chamber that holds the air. The outer sleeve protects it, which is why the bag must never be inflated without it.
Sealed seams
The point that carries the pressure. Do not step on them, do not fold them over sharp edges and never exceed the working pressure.
3. Choosing the bag: the maximum-void formula
The rule that tells you whether your bag fits a gap. The largest void a bag can safely fill is worked out from its width — the smaller dimension. If the gap is wider, the bag will not apply pressure properly and will work its way out in transit.
Maximum void = (width ÷ 2) − 5 cm
For the 90 × 180 bag: (90 ÷ 2) − 5 = 40 cm. The 180 cm length defines how much cargo height it covers, not the void.
| Size | Width | Maximum void | Height it covers |
|---|---|---|---|
| 60 × 90 cm | 60 cm | 25 cm | Low loads |
| 90 × 120 cm | 90 cm | 40 cm | Medium loads |
| 90 × 180 cm | 90 cm | 40 cm | Tall loads |
| 90 × 220 cm | 90 cm | 40 cm | Very tall or heavy loads |
Every 90 cm wide bag shares the same 40 cm maximum void: what changes with the length (120 → 180 → 220) is the cargo height it spans. That is why the 90 × 180 is the choice for long voids with tall cargo. Confirm working pressure and level with your SECAL adviser.
Measure the width of the void at its widest point, between cargo and cargo or between cargo and wall — that number rules everything else. The bag should cover at least two thirds of the height of the package it stabilises, and must never be taller than the cargo, or it balloons over the top and loses its grip.
4. Installation, step by step
1. Stow tight from the back
Place each row against the one before, working from the back of the container towards the doors. Concentrate the voids in the centre rather than spreading them around.
2. Protect corners and sharp edges
If the cargo has edges, strapping or rough surfaces, put cardboard, corrugated board or a rigid buffer between the cargo and the bag. One puncture and the bag is useless. No point or sharp edge should touch it: the contact face must be flat and wide.
3. Position the deflated bag
Lay it flat, centred in the gap, valve facing the doors so you can inflate and deflate it comfortably. Do not fold it or kink the valve. Carry it in your arms to the void — never drag it along the container floor, which scrapes and perforates the fabric.
4. Inflate with compressed air
Couple the inflation gun to the valve and inflate progressively until the bag presses the cargo against the walls and feels firm. Stand to the side, never in front of the bag, and wear eye protection. Use an inflator with a gauge and never exceed the working pressure printed on the bag.
5. Check firmness and look for leaks
Press with your palm: a properly inflated bag barely gives. It must fill the whole width and height of the void with no gaps. Check that the valve seals and that there is no hiss of escaping air.
5. The right pressure: neither slack nor over-inflated
Pressure is where most mistakes happen, and both extremes fail. A slack bag lets the cargo move; an over-inflated one can burst, deform the goods or build dangerous force against the doors.
1. The palm test
Push with an open palm: it should feel firm and give about 1 cm at most. If it sinks a long way it needs air; if it is rock hard it has too much.
2. The knuckle test
Tap it with your knuckles: a properly inflated bag sounds like a firm drum, not a slack hollow — like a well-inflated ball.
3. Full contact
Look at it head on: the bag must touch the whole face of the cargo, with no gaps above, below or at the sides. Gaps mean uneven pressure.
Rule of thumb: the force of the bag should be equal to or greater than the weight of the product it stabilises. When in doubt, firm beats slack — but never to the point of deforming the cargo or bulging the bag above the edge of the load.
6. Do this, not this
Do this
- Bag centred in the void, covering most of the cargo height
- Against flat, wide surfaces, with protective board at any edge
- Valve accessible, facing the doors
- One bag per void
- Carried in your arms to the void
Not this
- A bag taller than the cargo: the air rises, it balloons and loses grip
- In contact with edges or strapping with no protection — a puncture is certain
- Two bags together or folded: they slide against each other and come out
- Between the doors and the cargo: the locking bars pierce it and it builds dangerous pressure on opening
- Dragged along the floor: the rough container floor scrapes and perforates the fabric
7. Safety first
- Do not use in air freight: cabin pressure varies and the bag can deflate or burst.
- Never over-inflate — it can burst and cause injury.
- Stand to the side while inflating, not in front of the bag, and wear eye protection.
- Never place it between the doors and the cargo.
- Open with care at destination: pressure may have built up.
- Deflate through the valve — never puncture it with a knife.
- Inspect reused bags: a pinhole or a weak seam is worse than using nothing.
8. Frequent questions
How many bags do I need per container?
It depends how many voids you have and how big they are. The rule is one void, one bag of the right size. Concentrate the gaps in the centre when you stow, to keep the number of bags down and the grip up.
Are they reusable?
Yes. The valve opens and closes many times. At destination, deflate through the valve, fold the bag flat and store it somewhere dry. Inspect it for punctures or weakened seams before reusing it.
What equipment do I need?
A compressed-air source — a dock compressor — and an inflation gun compatible with the valve, ideally with a gauge. SECAL can supply the inflator with your order.
Do they replace strapping?
Not always; they complement it. Strapping holds each load unit together, and the air bag removes the void between units. Together they give integrity at package level and stability at container level.
How do I know if the void is too wide for the 90 × 180?
Use the formula: maximum void = (width ÷ 2) − 5. For this bag the width is 90 cm, so the gap must not exceed 40 cm. If it is wider, do not stretch the bag — reduce the gap with filler material or split the cargo into smaller voids.
Long voids, tall cargo?
We help you work out the exact quantity and the strength level for your route and your goods.
This guide is a reference. Confirm product, dose and placement with your SECAL adviser according to your cargo and route. SECAL technical guides · PROTEXPO S.A.C. / SECAL, Lima, Peru.