# Barrier bags

Select barrier packaging by moisture transmission, electrical protection, corrosion mechanism, closure integrity, and the complete packed system.

Reviewed: 2026-11-01

Tags: delivery, packaging, moisture-control

Specify moisture transmission, discharge shielding, oxygen transmission and corrosion inhibition separately. Desco lists moisture transmission, shielding, surface resistance and puncture resistance as separate properties. [Desco, *Bag Selection Chart*](https://desco.descoindustries.com/pdf/bagselectionchart.pdf)

As a bounded combined-function example, **SCS Dri-Shield 3700** uses polyester, foil, and polyethylene layers. Its September 2019 drawing describes the metal layer's discharge-shielding role, lists shielding energy below 10 nJ under ANSI/ESD STM11.31, and describes heat-sealable construction suitable for vacuum packaging. These are named-product data, not characteristics of every foil bag. [SCS, *Dri-Shield 3700 drawing*, September 2019](https://www.descoindustries.com/pdf/Dri-Shield-3700-Moisture-Barrier-Bag.pdf)

## Distinguish the protection mechanisms

| Function | What to establish | What it does not establish alone |
|---|---|---|
| Moisture barrier | Water-vapor transmission, conditions, material construction, and closure | ESD shielding or a guaranteed dry storage period |
| ESD protection | Applicable surface-resistance and discharge-shielding properties | Low water-vapor transmission |
| Vapor corrosion inhibitor (VCI) | Inhibitor product, protected metals, enclosure, and compatibility | A specified electronics dry-pack humidity or electrical shielding |

Desco's chart gives separate entries for shielding bags, moisture-barrier bags, and VCI packaging; some properties are marked not applicable. Treat each performance claim as a separate selection requirement rather than substituting one bag category for another. [Desco selection chart](https://desco.descoindustries.com/pdf/bagselectionchart.pdf)

VCI works differently. Cortec's **VpCI-126 Vacuum Bags** data sheet describes inhibitor molecules forming a protective film on metals inside an enclosed package, alongside additional moisture and oxygen barrier properties. Its listed metals include carbon steel, aluminum, copper, and brass. That product-specific corrosion claim is not evidence that any VCI formulation suits every alloy, coating, electronic assembly, or downstream cleanliness requirement. [Cortec data sheet, revision printed as 05/06/21](https://www.cortecvci.com/Publications/PDS/VpCI-126-Vacuum-Bags.pdf)

## Read transmission rates with their conditions

Water-vapor transmission rate (WVTR, sometimes labeled MVTR) expresses vapor transfer per area and time under stated conditions. ASTM F1249-25 covers flexible films and sheets, including multilayer materials, using a modulated infrared sensor. ASTM emphasizes agreement on test conditions and acceptance criteria and cautions that simple proportional relationships with thickness or vapor-pressure difference may not always apply. A method number alone does not supply the missing temperature or humidity conditions. [ASTM F1249-25, updated November 10, 2025](https://store.astm.org/standards/f1249)

For example, Cortec's cited VpCI-126 Vacuum Bags sheet reports **0.0043 g/100 in²/24 hours**, also shown as **0.067 g/m²/24 hours**, under ASTM F1249 at **100.4°F (38°C), 90% RH**. Preserve those printed conditions; do not reinterpret the reported humidity as a fully specified humidity differential without the test details. [Cortec, typical-properties table](https://www.cortecvci.com/Publications/PDS/VpCI-126-Vacuum-Bags.pdf)

**Illustrative arithmetic only:** if a hypothetical package has 0.5 m² total exposed film area and that film maintains a rate of 0.067 g/m²/day, 30 days corresponds to `0.067 × 0.5 × 30 = 1.005 g` through the film. This assumes constant applicable test conditions and excludes seals, holes, trapped moisture, and moisture released by contents. It is neither a desiccant-sizing calculation nor a storage-life prediction. Include both faces and any gussets when defining area.

Compare rates only after matching units, temperature, humidity conditions, specimen treatment, and material configuration. Keep film data separate from claims about a complete sealed package or a package after transit.

## Desiccant and indicators form a system

Desco's **TB-2031, September 2026**, combines a moisture-barrier bag, desiccant, and humidity indicator card (HIC) for electronics dry packaging and refers users to IPC/JEDEC J-STD-033D procedures. Desiccant reduces moisture inside the closed space; the bag limits further ingress. The cited card's indicating spots change reversibly with humidity, so it should not be treated as an irreversible record of every previous exposure. [Desco TB-2031, pages 1–2](https://www.descoindustries.com/pdf/TB-2031.pdf)

Sizing depends on the required humidity and package conditions. The same bulletin states equilibrium water uptake for a desiccant unit at specified temperature and RH; a “unit” is therefore not a universal number of grams of usable water capacity under all conditions. Do not use the simplified film calculation above as the entire moisture load. [Desco TB-2031](https://www.descoindustries.com/pdf/TB-2031.pdf)

Desiccant handling matters before sealing. Clariant's October 20, 2026 guidance explains that exposure to ambient air consumes available adsorption capacity and recommends promptly resealing the supply package. Keep handling limits and storage instructions tied to the selected desiccant rather than assuming unopened and long-exposed pouches perform equally. [Clariant, *Desiccant handling and moisture protection*](https://www.clariant.com/en/Corporate/Blog/2026-Blog-Posts/10/Desiccant-handling-moisture-protection)

## Closure integrity and physical protection

Choose a bag large enough for the product and closure, with protection against sharp features and movement. Review puncture and flexing risks separately from nominal thickness. For the Dri-Shield 3700, the supplier gives product-specific sealing temperature, dwell, and pressure conditions. Those settings describe that material and require an appropriate sealing process; they are not a universal recipe for other laminates or sealers. [SCS drawing](https://www.descoindustries.com/pdf/Dri-Shield-3700-Moisture-Barrier-Bag.pdf)

Seal strength, visible seal condition, and leakage answer different questions. ASTM's packaging committee identifies F88 for seal strength, F1886 for visual seal inspection, and F2096 for gross-leak detection by internal pressurization. Select applicable methods and acceptance criteria for the package; passing one does not establish every other barrier property. These references do not designate an ordinary industrial bag as a sterile medical barrier. [ASTM Committee F02, packaging test-method overview](https://www.astm.org/v3/assets/blt5eb0a2cb04534832/blt05255f89f20c8e7c/69d75db6b4fda0e746ff4394/F02-Fact-Sheet-2025.pdf)

For a practical packing instruction, identify the bag part number and document revision, protected item, closure process, desiccant/HIC requirements, inspection criteria, storage environment, and action after opening or damage. Confirm that cushioning, labels, and handling preserve the selected protection. A material specification is one input to that instruction, not a substitute for evaluating the packed assembly.

Related: [Desiccant packaging](desiccant-packaging.md) · [ESD packaging](esd-packaging.md) · [VCI packaging](vci-packaging.md) · [Delivery guides](../index.md).