Quick Answer: A dunnage bag for container load securing in Ontario is an inflatable polywoven or kraft-paper bag pressed into the void between pallets, inflated to 2-3 PSI for standard bags or up to 30 PSI for AAR Level 4-5, that braces cargo against ocean roll, rail switch shock, and Highway 401 jostle. The bracing conversation happens at quote stage, well before your container reaches your site. Van Blanc has shipped containers across Ontario since 1995. Honest 4.9-star service, 1-3 day delivery from 4 Brantford yards.
In This Guide
- Why Does Void Fill Matter in a Sealed Container?
- Paper or Polywoven: Which Dunnage Bag Should You Choose?
- What Are the AAR Dunnage Levels (1 to 5)?
- What PSI Should You Inflate a Dunnage Bag To?
- What Size Dunnage Bag Fits the Void?
- Where Do Dunnage Bags Go Inside a 20ft and 40ft Container?
- What Inflation Equipment Does a Yard Need?
- What Mistakes Break Loads in Transit?
- How Does Ontario Freight Shape Dunnage Decisions?
- What Does Van Blanc Supply on a Load-Secured Sale?
- Frequently Asked Questions
Reading time: about 13 minutes.
Why Does Void Fill Matter in a Sealed Container?
Void fill matters because empty space inside a sealed container is where cargo builds momentum and breaks. A dunnage bag, inflated into the gap between pallets, applies even pressure on both sides, so the load has to compress the bag before it can shift. That is the difference between an intact shipment and broken cases at the dock.
A sealed 20ft or 40ft looks calm when the doors close. Two hours later, that container is doing 90 km/h on Highway 403 east of Brantford, and the pallets that looked tight in the yard are shifting four to six inches per kilometre. By the time the box reaches the consignee, the pallets have walked into the door wall, the corner protectors have crushed, and a packing list of broken cases is waiting at the receiving dock.
That story repeats every week across Ontario. It is why we keep a full reference on lashing, bracing, and Transport Canada Standard 10 on hand, and the reason a polywoven dunnage bag, sized right and inflated correctly, is the single highest-leverage tool a shipper has for preventing in-transit damage. Strapping holds pallets vertically; corner protectors stop edge crush; friction mats keep pallets from sliding on the deck. None of those tools fill the cubic-foot void between two pallets the way an inflated bag does.
A 20ft has roughly 33 cubic metres of internal volume; a 40ft has 67. Pallet cargo rarely fills that volume tightly. Any void over four inches wide is where cargo builds kinetic momentum during a port crane lift, a rail switch, or a sudden stop on the 401. A dunnage bag expands into that void and applies even pressure on both sides, so when the cargo wants to shift, it has to compress the bag first.
Paul LeBlanc, owner: “After nineteen years in this industry I can tell you the load that arrives wrecked is almost never wrecked by the steel. It is wrecked by the air. Fill the void properly and most claims never happen. Skip it and the pallets walk every time.”
How a Dunnage Bag Actually Works
A dunnage bag is a polyethylene inner bladder inside a woven polypropylene or kraft-paper outer shell, with a valve at one corner. Folded flat in storage, placed in the void, inflated through the valve using a compressor or hand pump. Internal pressure (typically 2 to 3 PSI for standard loads, higher for heavy-duty applications) creates a uniform clamping force across the contact area. When the truck brakes hard, the cargo pushes into the bag, the bag compresses slightly, air pressure rises momentarily, then returns to baseline once the impulse passes.
Paper or Polywoven: Which Dunnage Bag Should You Choose?
Choosing between paper and polywoven dunnage bags comes down to load weight, moisture exposure, shipping mode, and whether you plan to reuse the bag. Two materials dominate the dunnage market: multi-ply kraft paper and woven polypropylene. A buyer who treats them as interchangeable will eventually choose wrong on a shipment that mattered.
Kraft paper bags have one advantage polywoven cannot match: a high coefficient of friction against most palletised surfaces. The paper outer grips corrugate, wood, and stretch-wrap better than polypropylene, which helps lock the load against the sidewall once inflated. For dry domestic over-the-road shipments, kraft paper is a strong, economical choice, typically single-use, and priced lower per unit.
Polywoven bags are the workhorse for everything harder. They are 60 percent lighter than kraft-paper equivalents, single-ply, and rated for higher pressures. The woven polypropylene outer resists punctures from staples, nail heads, and broken pallet edges. Moisture, which degrades kraft paper rapidly, has no meaningful effect on polypropylene. Polywoven bags are reusable: a well-stored bag handles ten to twenty cycles before retirement.
| Property | Kraft Paper | Polywoven Polypropylene |
|---|---|---|
| Friction against pallet | High (best in class) | Moderate |
| Weight per bag | Heavier (multi-ply) | 60% lighter (single-ply) |
| Pressure rating | Lower (2-3 PSI typical) | Higher (up to 30 PSI on Level 4-5) |
| Moisture tolerance | Poor | Excellent |
| Reusability | Generally single-use | 10-20 cycles |
| Cost per unit | Lower | Higher up front, lower per cycle |
| Best for | Dry over-the-road, light loads | Ocean, intermodal, heavy, humid |
| Sustainability | Recyclable with corrugated | Recyclable as PP, reusable |
For an Ontario buyer loading a 40ft that will move from a Brantford yard to a Vancouver port and onward by ocean to Asia, polywoven is the only honest answer. For a 20ft going across Highway 403 to a Hamilton receiver with dry corrugated cases, kraft paper does the job at a lower cost.
What Are the AAR Dunnage Levels (1 to 5)?
The AAR dunnage levels are a five-tier rating that matches a bag’s restraining force to the load it has to hold, from Level 1 for light palletised goods up to Level 5 for the heaviest rail-only industrial freight. The Association of American Railroads runs this dominant North American certification programme for pneumatic dunnage. The standard most often referenced is GIB No. 9 (Product Performance Profile for Pneumatic Dunnage), and RP-4 governs how bags perform under pressure during verification testing. A buyer asking about the older “M-921” rail standard is asking about the same body of work; the AAR regime has consolidated under the GIB and PPPPD documentation.
Verification is not a one-time event. AAR re-verifies pneumatic dunnage every three years, and bags that fail come off the approved list. A railroad will reject a car secured with non-verified bags, and the damage claim falls back on the shipper. For Ontario shippers moving freight by CN or CP rail, AAR verification is the gating compliance question.
The five levels exist because not every load needs the same restraining force. Heavy machinery on a flatcar needs Level 4 or Level 5. Light palletised consumer goods in an intermodal box may be fine with Level 1 or 2. Picking too low a level invites burst failure. Picking too high adds cost without buying additional safety.
Reading the AAR Label
Every AAR-verified bag carries a permanent label showing manufacturer, level (1 through 5), production date, and maximum inflation pressure. Inspect the label before any rail shipment. Missing, illegible, or past the three-year re-verification cycle means non-compliant. Store bags in dry, dust-free conditions to keep labels readable.
What PSI Should You Inflate a Dunnage Bag To?
Inflate a standard polywoven or kraft-paper dunnage bag to 2 to 3 PSI for over-the-road palletised freight, and climb into the 8 to 30 PSI range only for heavy intermodal and rail loads on Level 3 to Level 5 bags. Wrong inflation pressure is the biggest avoidable mistake. Under-inflate and the bag does not fill the void; the cargo shifts. Over-inflate and the bag pushes the cargo apart, transfers force into the pallets, and risks bursting on the first switching impulse.
Standard polywoven and paper bags for over-the-road freight operate at 2 to 3 PSI. The void is small (typically four to twelve inches) and the cargo is reasonably stable on its own. For heavier intermodal and rail applications the pressures climb: Level 3 bags hold 8 to 25 PSI, Level 4 bags 10 to 30 PSI, Level 5 bags higher still for the heaviest steel-and-machinery loads.
| Application | Bag Level | Min Inflation | Max Inflation | Typical Use |
|---|---|---|---|---|
| Light pallet OTR | Standard paper/polywoven | 2 PSI | 3 PSI | Corrugated case freight, light pallet |
| Medium pallet intermodal | Level 1-2 polywoven | 3 PSI | 8 PSI | Consumer goods, ocean export |
| Heavy palletised | Level 3 polywoven | 8 PSI | 25 PSI | Drums, bulk product, dense cases |
| Heavy industrial | Level 4 polywoven | 10 PSI | 30 PSI | Machinery, steel coils, heavy parts |
| Maximum severity | Level 5 polywoven | 15 PSI+ | 40 PSI+ | Rail-only heavy industrial |
The gauge is the single most important tool. A worn gauge invites under-inflation or burst-risk over-inflation. Calibrate monthly if the yard ships heavy daily; replace any that drift more than 0.5 PSI from a known-good reference.
What Size Dunnage Bag Fits the Void?
The right dunnage bag size is one that fills the actual void snugly without stretching to the edge of its inflated envelope. Matching bag size to the void is the second-biggest avoidable mistake. The bag should fit snugly, not stretched to its limits and not so loose that it has to expand a long way to make contact. A bag stretched to maximum is operating at the edge of its design envelope and is prone to seam failure. A bag too small has to over-inflate to reach the cargo, moving it outside the safe pressure range.
Manufacturer charts give the inflated dimensions against void widths. A 36-by-48-inch bag typically fills voids four to eight inches wide. A 48-by-96-inch bag covers a taller pallet stack in the same width range. The tolerance is narrower than buyers expect, which is why yards stocking varied freight keep several bag sizes on the shelf.
A Real Yard Example
A Brantford-area frozen-food shipper loads 40ft high-cube containers with palletised cases bound for Vancouver. Each container holds 20 standard pallets stacked two high. The void between side rows averages five inches; the void at the doors averages eight. The shipper uses 36-by-60-inch polywoven Level 2 bags for the side voids and 48-by-72-inch Level 2 bags for the door void. Inflated to 4 PSI, the bags stay seated through rail, ocean, and final road delivery. Spread across seven or eight reuse cycles, the per-shipment cost of those polywoven bags drops to a fraction of what a single damaged pallet would cost to replace.
Where Do Dunnage Bags Go Inside a 20ft and 40ft Container?
Dunnage bags go wherever a void lets cargo build momentum: between centre rows, against the rear doors, and along the side walls when pallets are narrower than the interior. Where the bags go inside a container is determined by the cargo configuration, not by habit. The default placement patterns work for most palletised freight and should be the starting point for any load plan.
In a 20ft loaded with 10 pallets in two rows of five, typical placement is a bag between the centre rows, a bag at the rear against the doors, and friction matting under any pallet that does not sit flush. For a 40ft with 20 to 22 pallets the pattern scales: a centre-column bag every five pallets in length, a rear bag, and friction matting under uneven pallets. Total bag count runs three to six in a 20ft and six to twelve in a 40ft.
Side-wall void filling is necessary when pallets are narrower than the interior. Two 40-inch-deep pallets fit side by side in a 92-inch-wide container with 12 inches of total void. Splitting that void with bags along both side walls prevents pallets from walking outward into the wall corrugations.
The vertical dimension matters too. A bag at the base of a pallet stack does nothing for the top if cases are not strapped together. For tall stacks, place bags at multiple vertical levels or use a vertical bag tall enough to engage the full stack height. Buyers loading 9-foot-6 high cube containers often need 72-inch or 96-inch tall bags rather than the standard 48-inch.
Worth the Drive: Picking Your Container from a Real Brantford Yard
Van Blanc operates four Brantford yards on Morton Avenue East. Ontario buyers from Hamilton, Niagara, the GTA, and the Waterloo-Wellington corridor regularly drive in to walk our rows before they buy. They want to see the CSC plate on the actual bin, check the floor before money changes hands, and confirm the container comes with realistic load-securement guidance, from bag selection through to strapping the load down with E-track and ratchet straps. Worth the drive for unbeatable quality, family customer service with 30 years of experience.
What Inflation Equipment Does a Yard Need?
A yard inflating dunnage bags needs an air-line-fed or 12-volt inflator with a calibrated gauge and a quick-disconnect valve, not a hand pump for anything past the occasional emergency. The right tool turns a slow process into a 30-second-per-bag routine. For yards with compressed air plumbed, an air-line-fed inflator with a calibrated gauge and quick-disconnect valve is the standard. Clip onto the bag valve, pull the trigger until the gauge reads target, release. Total time: 20 to 40 seconds per bag. For yards without compressed air, a battery or 12-volt-DC inflator off the truck electrical system handles the same task in 60 to 90 seconds.
Hand pumps work for emergencies but are slow (three to five minutes per bag) and prone to under-inflation. A yard moving more than two loads a day should never rely on one.
Christian LeBlanc, second-generation operator: “Buyers will invest in a clean one-trip 40ft and then try to shave the dunnage off the load to save a few bags. The container arrives, the pallets have walked, the cargo is damaged, and now they are calling about a claim. The bracing is the cheapest insurance on the whole shipment. It is not the place to cut.”
What Mistakes Break Loads in Transit?
The mistakes that break loads in transit are predictable: six failure modes account for nearly all dunnage-related load damage.
Wrong bag for the route. Kraft paper on an ocean shipment degrades in container humidity and burst-fails during the voyage. Specify polywoven for ocean, rail, or intermodal routes; reserve paper for dry over-the-road.
Under-inflation. The bag looks full but is below rated pressure. The cargo shifts on the first hard stop. Fix: calibrated gauge and a trained loader.
Over-inflation. The bag is past rated pressure and bursts on the first impulse load. The cargo hits the door wall at full kinetic energy. Fix: the same gauge plus respect for the bag’s printed maximum.
Wrong bag size for the void. Too small leaves a gap; too large operates at the edge of its envelope. Fix: stock multiple sizes and measure the actual void on the actual load.
Sharp edges in contact with the bag. Broken pallet boards, exposed staples, or sharp case edges puncture the bag in transit. Fix: corner protectors or padding.
Expired or non-AAR bags on rail freight. The railroad rejects the car or the claim fails. Fix: check the verification label before every rail load and rotate older bags out as the three-year cycle approaches.
Pre-Departure Dunnage Check
- Bag material matches route (polywoven for ocean/rail/humid; paper for dry OTR)
- AAR level matches load weight (1-2 light, 3-4 heavy, 5 industrial)
- Pressure reads within printed min-max on a calibrated gauge
- Size fills the void without stretching past 80 percent of inflated dimension
- Sharp edges shielded by corner protectors or padding
- Label legible and inside the three-year verification window
How Does Ontario Freight Shape Dunnage Decisions?
Ontario freight shapes dunnage decisions through three local realities: hard braking on the congested 400-series highways, heavy CN and CP intermodal switching, and long ocean-export legs out of Halifax, Montreal, and Vancouver. Ontario freight has three character markers that influence dunnage choice. The first is the 400-series highway network: Highway 401, Highway 403 through Hamilton and Brantford, the QEW around Niagara. Well maintained but congested, with frequent hard braking around the GTA. Loads through the GTA core face more impulse events per kilometre than rural freight, so dunnage gets worked harder.
The second is intermodal volume. Ontario sits at the CN/CP main-line intersection, with intermodal terminals handling thousands of containers per week. Rail switching impulses reach 8 mph and humping forces add more. AAR-verified bags are not optional. A yard sending freight by intermodal needs Level 2 or higher polywoven bags as the baseline.
The third is ocean export to Halifax, Montreal, and Vancouver. A 40ft loaded in Brantford might roll on the 401 to Hamilton, transfer to rail, ride 4,000 kilometres to Vancouver, then sit on a vessel deck for two weeks of ocean roll before discharge in Asia. Polywoven Level 2 to Level 4 bags, sized to the void and inflated to spec, keep that load intact through every leg.
Van Blanc has been delivering containers across this network since 1995. Buyers who call us are asking which container, which grade, and how to set it up for the journey their cargo is taking. Thirty years of seeing what works and what fails on real Ontario loads is what shapes our recommendations.
What Does Van Blanc Supply on a Load-Secured Sale?
Van Blanc supplies the container and the load-securement plan that goes with it: the right grade for the route, the void geometry your cargo creates, and the bag material, sizes, and inflation targets that match. A container is not a finished load-securement package on its own. When a customer buys a 20ft or 40ft from our Brantford inventory with intent to ship loaded cargo immediately, the bracing-and-dunnage conversation happens at the quote stage, not after delivery.
What that conversation covers every time:
- Container grade fit for the route (a factory-paint new build for an export run, Cargo Worthy for re-export, Wind & Watertight for stationary storage)
- Expected void geometry (pallet count, stack height, side-wall gaps)
- Bag material and level for the route (polywoven for ocean/rail; paper for dry OTR)
- Recommended sizes and quantities (three to six for a 20ft, six to twelve for a 40ft)
- Inflation pressure target and gauge requirement
- Strapping, corner protection, and friction matting as complements
- Real lead time on the container, not a hopeful one
Some buyers handle their own dunnage sourcing and just need the container. Others want us to point them at a trusted supplier in the Hamilton-Brantford corridor. Many people call us saying they can get a bin less on Facebook. Two weeks later they call back saying they got scammed. Worth the drive for unbeatable quality, family customer service with 30 years of experience.
Ready to price your container?
Tell us the size and your postal code and we’ll send back an honest, all-in number, container, delivery, and placement, usually within 1-3 days. No pressure, no mystery fees.
Family-run in Brantford since 1995 · 200+ containers in stock · 4.9★ across 124+ Google reviews · every box graded by a person, walk it before it lands.
Frequently Asked Questions
What is a dunnage bag and what does it do inside a shipping container?
A dunnage bag is an inflatable bag, typically polywoven polypropylene with a polyethylene inner bladder or multi-ply kraft paper, that fills the void between pallets or cargo and a container wall. Inflated to 2 to 3 PSI for standard loads or up to 30 PSI for AAR Level 4 applications, it braces the load against ocean, rail, intermodal, or over-the-road movement.
What PSI should a dunnage bag be inflated to?
Standard paper and polywoven bags for over-the-road palletised freight operate at 2 to 3 PSI. AAR Level 3 bags handle 8 to 25 PSI. Level 4 bags handle 10 to 30 PSI for industrial machinery and steel. The exact pressure is printed on the bag and should be read with a calibrated gauge.
Are dunnage bags reusable?
Polywoven polypropylene bags are reusable, running 10 to 20 cycles before retirement when stored dry and inspected between uses. Kraft paper bags are generally single-use and recycled with corrugated cardboard. For Ontario shippers running regular ocean export cycles, polywoven reuse drops per-shipment cost dramatically.
Is paper or polywoven the better material for ocean shipping?
Polywoven, every time. Ocean shipments face two weeks or more of vessel roll and humid container interiors. Kraft paper degrades in moisture and burst-fails under prolonged ocean stress. Polywoven polypropylene is unaffected by moisture and carries the higher pressure ratings needed for ocean and intermodal compliance.
What is AAR verification and why does it matter for rail freight?
The AAR verifies pneumatic dunnage against the GIB No. 9 Product Performance Profile and RP-4 standards. Verified bags carry a label showing manufacturer, level (1 through 5), and date. CN and CP rail rejects loads secured with non-verified bags, and damage claims fail when bags are not on the verification list. Re-verification happens every three years.
How many dunnage bags does a 20ft or 40ft container typically need?
A 20ft loaded with 10 palletised units typically uses three to six bags: one or two centre-row, one rear-wall, and bags along the side walls if pallets are narrow. A 40ft with 20 to 22 pallets typically uses six to twelve. Exact count depends on void geometry and bag size, which is why we walk through the cargo plan at quote stage.
What size dunnage bag do I need?
Match inflated dimensions to the actual void. A 36-by-48-inch bag typically fits voids four to eight inches wide. A 48-by-96-inch bag covers taller stacks at the same widths. The bag should fill the void snugly without stretching past 80 percent of its rated inflated dimension.
Can I use dunnage bags with sharp-edged cargo like machinery or steel coils?
Yes, with corner protectors, padding, or sleeve material between the sharp edge and the bag surface. Bare contact punctures the bag during the first hard stop. For heavy industrial freight, AAR Level 4 or Level 5 polywoven bags combined with proper edge protection are the standard.
What inflator tool should I use?
Yards with compressed air should use an air-line-fed inflator with a calibrated gauge and quick-disconnect valve. Yards without plumbed air can use a 12-volt-DC inflator off the truck electrical system. Hand pumps work for emergencies but are too slow and prone to under-inflation for regular use.
Does Van Blanc supply dunnage bags with a container sale?
Dunnage bag supply is not a default line item, but the conversation about which bags, sizes, and inflation targets happens at quote stage. We can point Brantford-area and Hamilton-area buyers to trusted suppliers. Call our Brantford yard at 519-754-6844 to walk through your specific load. Real lead time, not a hopeful one.
Sources
- International Organization for Standardization. (2022). ISO 6346:2022, Freight containers: Coding, identification and marking. iso.org/standard/82754.html
- Transport Canada. (2025). Cargo Securement Standard 10: Containerized Cargo. tc.canada.ca
- Association of American Railroads. (2017). General Information Bulletin No. 9: Product Performance Profile for Pneumatic Dunnage. aar.com/standards
- Association of American Railroads. (2024). Pneumatic Dunnage Product Verification List (Table 12.1). aar.com
- International Maritime Organization. (1972, amended). International Convention for Safe Containers (CSC). imo.org
Reach Van Blanc in Brantford
We have supplied shipping containers across Ontario since 1995. Our warehouse is at 90 Morton Avenue E in Brantford, and we deliver across the province on a cash-on-delivery basis. No surprise fees.
Van Blanc Ent. Inc., 90 Morton Ave E Unit 1B, Brantford, ON N3R 7J7, +1 888-509-6658
Loading a 20ft or 40ft for an Ontario route or an ocean export? Call our Brantford yard at 519-754-6844 and we will walk through void geometry, bag selection, and inflation plan before you finalise the container. Real lead time, not a hopeful one.