ASTM F1249: Moisture Vapor Transmission Through Packaging Film
A sterilization pouch that lets humidity drift through its film is still sealed, still labelled as sterile, and still a problem if the contents are moisture sensitive. ASTM F1249 is the test method that puts a number on how much water vapour crosses a packaging film.
Reading that number correctly takes a little context, because a film property is not the same thing as a finished package.
What does ASTM F1249 measure?
The method measures water vapour transmission rate, usually shortened to WVTR. A film sample is clamped in a cell, one side is held at a controlled humidity, and dry gas sweeps the other side. An infrared sensor detects the moisture that crosses the film, and the result is reported as a rate per unit area per day.
Because the sensor responds to water vapour directly, the test runs faster than older cup methods and gives a steady-state figure rather than an average over days.
How is the result reported?
| Result element | What it tells you | What it does not tell you |
|---|---|---|
| Transmission rate | How much vapour crosses a given area per day | How the finished pouch performs after sealing |
| Test conditions | Temperature and humidity the sample saw | Whether your storeroom matches those conditions |
| Film orientation | Which side faced the humid chamber | How the material behaves when folded or creased |
| Method reference | Which standard was used | Whether the supplier also tested seal integrity |
Two films can carry similar labels and very different rates, so the number only becomes useful when the method and the conditions travel with it.
Where does moisture actually cause trouble?
The risk is rarely a dramatic failure. It shows up as packaging that feels soft in a humid summer, as moisture-sensitive indicators that change appearance before the load is used, or as a stored kit whose contents have stuck together. In a Canadian clinic the swing between a humid July and a dry January heating season is exactly the condition that makes storage practice matter.
Which products does it apply to?
Packaging lines are where the film discussion lands. Class 4 sterilization pouches pair a transparent film with a porous paper side, and sterilization roll uses the same film concept in a cut-to-length format. For loads that carry Bowie-Dick test packs, keeping the carton closed and the storeroom stable does more for the indicator than any property of the film.
How should a buyer use WVTR data?
Treat it as one input rather than a ranking. Ask the supplier which method produced the figure, whether the film was tested in the same orientation your pouch uses, and how the pouch was validated for shelf life. Then look at your own storage: a closed drawer in a climate-controlled room will hold a sterile presentation far longer than an open shelf beside a sink.
If you are comparing packaging lines for a clinic or a group of clinics, start with the five-pack biological indicator trial at CA $12.99 with shipping included to confirm your cycle first, then request a packaging quote sized to your monthly load count.
References
- ASTM F1249 - Standard test method for water vapor transmission rate through plastic film and sheeting using a modulated infrared sensor (checked 19 September 2026)
- ASTM F1980 - Accelerated aging of sterile barrier systems (checked 19 September 2026)
- Public Health Ontario - infection prevention and control guidance for clinical settings (checked 19 September 2026)
Related Reading
- Sterilization monitoring supplies for Canadian clinics
- Learning Hub - clinical and procurement guides
- Wholesale and multi-site ordering
- Sterile packaging alternatives: paper, film and reusable options
- Seal integrity testing for sterile pouches: ASTM F88, F1929 and F1886
- What is roll gaine and is it a sterilization pouch?
- free Ontario sterilization compliance log
- printable autoclave sterilization log sheet (free)
Frequently Asked Questions
What does ASTM F1249 measure?
It measures the water vapour transmission rate of a plastic film or sheeting. A sample is mounted so one side faces a controlled humidity while the other side is swept by dry gas, and a sensor counts the moisture that crosses the film. The result is reported as a rate per unit area per day.
Why would a clinic care about WVTR?
Sterile barrier packaging has to keep its contents dry as well as sterile. A film that passes moisture easily can let humidity reach the contents during storage, and moisture is one of the conditions that can spoil a sterile presentation or damage a moisture-sensitive device.
Does a lower WVTR always mean better packaging?
Not by itself. Barrier performance, seal strength, tear behaviour and how the package is opened all matter, and a film with an excellent moisture barrier can still be wrong for a load if it does not seal well on your machine.
Is F1249 the same as the older ASTM E96 method?
They are different methods. ASTM E96 uses a gravimetric approach with a cup, while F1249 uses an infrared sensor and a controlled flow of dry gas. Results from the two methods are not interchangeable, so compare numbers only when the method matches.
Last updated: September 2026. CliniEco Medical holds MDEL #35334 issued by Health Canada, and supplies clinics, long-term care homes and home-care programs across Canada.
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