In a steam autoclave, the paper side of a sterilization pouch faces up. Steam and heat enter the package through the porous paper layer, while the clear film is the barrier that should sit against the rack, tray or instrument below it. Load every pouch paper-side up so steam moves into the package and condensate drains away instead of pooling against plastic.
Quick facts
- Paper is the permeable layer; film is the barrier layer.
- Steam enters through paper, so paper faces up in the chamber.
- A pouch loaded film-side up traps condensate under the plastic.
- Class 4 dual-indicator pouches stay readable through the film after the cycle.
- The rule holds whether a pouch lies flat or stands in a holder.
Why the paper side has to face up
In a steam cycle the chamber air is removed and replaced with saturated steam. The medical-grade paper layer lets that steam through while still filtering particles once the package is dry. Film is not permeable, so when paper is not exposed to the steam path, vapour has to find another route in and often does not reach the contents evenly.
Orientation also decides how the load drains. Condensate forms on every surface and gravity pulls it down; with paper up, moisture on top of the pouch can evaporate during the dry phase. With film up, water beads on the plastic and sits over the seal line and the indicator.
What happens when a pouch goes in film-side up
Most teams notice the problem after the cycle. The pouch comes out with droplets inside the film or a milky haze where moisture sat against the barrier, and sometimes it peels open along a wet seal — and the seal line is what keeps the contents sterile.
A wet film side also makes an indicator harder to read. An uneven colour change is a reading problem rather than proof of a failed cycle, but it is enough to make a load hard to release with confidence. Check orientation, spacing and dry time before you look for a mechanical fault.
Orientation by load type
The table below is the version we hand to new staff, and it covers the four packages that show up in a typical dental or clinic load.
| Load type | What faces the steam | What to watch |
|---|---|---|
| Loose instruments in a pouch | Paper side up | Leave a gap so steam circulates |
| Pouch standing in a rack | Paper toward the steam path | Do not press film against a solid divider |
| Pouch on a flat tray | Paper up, film against the liner | Never stack pouches on each other |
| Roll stock cut to size | Paper side up | Seal, label, load like any package |
If the pouch is part of a wrapped set or a rigid container load, the same logic applies to the permeable panel: face the steam, stay clear of anything solid.
Cassettes, racks and tight loads
A heavier cassette changes the loading plan, not the pouch rule. A pouched cassette should lie flat, paper up, with room so a hinge does not crease the barrier. Creases are a common failure point because the fold rubs a hard edge through the cycle.
When pouches stand on edge, keep them from leaning on each other: film against film blocks the steam path. Follow your sterilizer maker's loading diagram for chamber capacity, then apply the paper-up rule so each package actually sees steam.
A five-second check before you close the door
Look across the finished load and confirm every pouch shows paper, not plastic, from above. Then check that packages are not touching, the chamber is not overloaded, and dry time matches the load.
Pair the habit with scheduled sterilizer verification. The CliniEco 24h Biological Indicator — 5-Pack Trial ships with shipping included, and the sterilization compliance hub collects the log templates that go with it.
Ordering for a clinic, lab or care home? Wholesale and multi-site ordering covers case pricing and account setup, and the B2B wholesale collection lists the lines stocked for institutional buyers.
Related reading
Three guides that answer the next questions clinics ask after orientation:
- Autoclave Pouch Sealing: 3 Common Errors and Their Root Causes
- Peel Pouches, Wrapped Sets or Rigid Containers: What Each Load Needs
- Sterilization Pouches Compared: Crosstex Sure-Check, Medline and Open Options
- printable autoclave sterilization log sheet (free)
- free Ontario sterilization compliance log
Frequently Asked Questions
Does the paper side always face up in every sterilizer?
For steam sterilization, yes — paper toward the steam path, film away from it. Follow your own sterilizer manual's loading diagram first.
What happens if I load a pouch film-side up?
Condensate pools against the plastic, drying slows, and the seal or indicator can come out wet and uneven.
Should pouches lie flat or stand on edge?
Either works if the paper stays exposed. Flat suits small pouches; racks save space but need spacing between packages.
CliniEco Medical is a licensed medical device establishment (MDEL #35334).
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