When discussing wet packs it is helpful to review the various pack configurations and their unique susceptibility to wetness. There are four primary pack types:
1. Paper/Poly or Steri-Peel
2. Paper/Poly or Steri-Peel
3. Disposable Wrap
4. Rigid Containers
Rule #1
All materials to be sterilized must be dry when loaded in to chamber for processing. Moisture loaded into the chamber will not be sufficiently removed during the cycle.
Rule #2
Containers, large instrument sets, and basin ware should be loaded on the lower shelf. Steri-Peel, towel packs, and light weight packs should be loaded on the upper shelf. Containers and instrument sets should never be stacked.
Condensate is formed as steam gives up its heat to the packs. The amount of condensate is proportional to the weight of the load. While the load heats up to the set point, temperature steam converts to water, rains to the chamber floor, and is mostly removed by the chamber steam trap. Residual water is flashed back to vapor by the heated jacket and removed by vacuum during the drying phase. If heavy instrument sets are placed on the top shelf, the lower shelf will experience a rain storm. 15 lb. instrument trays will condensate about a cup of water while heating from 70° F to 270° F.
Rule #3
Pools Inside of Packs
Are formed in closed end vessels not positioned to drain.
- Basins
- Eye Cups
- Tubing
- Cup Shaped Instruments
- Small Trays
Rigid containers should be prepared with a muslin wrap in the bottom to wick moisture over a large surface area to enhance drying.
Pools Outside of Packs
These pools are formed by poor loading technique. Folds and creases of disposable wrap will hold and pool water. Care should be given to positioning these packs to minimize pooling.
Steri-peel should always be positioned on edge and separated in a rack (similar to a letter rack) to allow condensation to drip off the bottom edge.
Water droplets on the outside of Steri-peel or disposable wrap is not desirable, but will not contaminate the pack. They should simply be blotted off with a cotton towel. Water repellency is the benefit of disposable wrap.
Muslin packs are typically easier to dry since muslin can absorb a lot of water and disperse it over a large surface. There can be a 20% moisture content in cotton before it feels wet.
If we could watch the sterilization process, we would see a dense fog caused by the continual phase change from liquid to vapor and vapor to liquid. Steam sterilization takes place in a saturated steam environment. Understanding pack construction and arrangement is the key to controlling wet packs.
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