Serving customers in the United States
Poly Mailers for Denver Businesses
Denver raises a packaging question almost nowhere else does: what happens to a sealed parcel when the air pressure around it drops. It matters on the ground here, and it matters again for anything travelling by air.
For most contents it is a curiosity. For a few — anything sealed, inflated or containing liquid — it is a real effect worth designing around.
Quote an order for Denver
Tell us what you ship and where it goes. We confirm the specification, the schedule and the price in writing.
Who buys mailers here
Sectors where poly mailers are genuinely the right packaging, with the reason each one appears rather than a generic list.
Outdoor and technical goods
A dense cluster of brands, many shipping products that are themselves sealed or inflatable.
Food and beverage
Direct-selling producers shipping sealed packaging that responds to pressure change.
Health and supplements
Sealed containers and pouches that behave differently at altitude.
What we would suggest
Poly Bubble Mailers
Bubble linings contain sealed air, which expands as pressure drops.
Read the detail
Padded Poly Mailers
Comparing cushioning types where an inflated lining is a consideration.
Read the detail
12x15 Poly Mailers
Room for contents that expand rather than a tight fit that resists them.
Read the detail
Self-Seal Poly Mailers
A seal under expansion pressure is tested differently from one under load.
Read the detailWhat actually happens
Air trapped in a sealed space expands as the surrounding pressure drops. That applies to the air inside a sealed food pouch, inside an inflated cushioning system, and inside a mailer sealed at sea level and delivered at altitude.
The effects are usually mild and occasionally not. A sealed snack pouch arrives visibly taut. An air-filled cushion becomes firmer than intended. A tightly sealed mailer with no slack can put its closure under pressure it was not designed to hold.
The mitigations are straightforward: leave a little slack rather than sealing a parcel absolutely rigid, prefer bubble linings over inflated void systems where a parcel will change altitude significantly, and be aware that this affects your suppliers’ packaging inside your parcel as much as it affects yours.
When this matters and when it does not
Four cases where it is worth thinking about, and the honest note that most shipping is not one of them.
Sealed pouches and containers inside the parcel
These are the contents that visibly change, and occasionally the ones that fail.
Air-filled cushioning
Systems inflated at low altitude become firmer higher up, which is usually fine and occasionally too firm.
Anything shipped by air
Cargo holds are pressurised, but not to sea level, so the effect is present on any air leg.
Everything else
Soft goods, garments, books, most accessories. The effect exists and does not matter.
Cushioning that does not inflate
Where a parcel will change altitude significantly and cushioning is required, a bubble-lined mailer behaves more predictably than an inflated void-fill system, because the volume of trapped air is small and distributed rather than concentrated in a few large cells. It is also lighter and takes less space in storage. The construction and how it protects is set out on the poly bubble mailer page.
Questions from Denver buyers
Does altitude affect poly mailers?
Only where air is sealed inside something. A mailer around soft goods is unaffected; sealed pouches, inflated cushioning and containers with trapped air all expand as pressure drops, which is usually visible rather than damaging.
Should I leave slack in a parcel shipped by air?
A little, rather than sealing it absolutely rigid. A parcel with no give puts its closure under expansion pressure it was not designed to hold, and a small amount of slack removes the effect entirely.
Is bubble lining better than air pillows at altitude?
It behaves more predictably, because the trapped air is distributed in many small cells rather than concentrated in a few large ones. It is also lighter and stores flat, which matters independently of altitude.
Ship at altitude
Tell us whether anything you ship is sealed, inflated or liquid. We will tell you honestly whether altitude is a consideration for you.