Sterile Storage, Event-Related Sterility, and Sterile Transfer

Why Sterile Storage Conditions Matter

Once a package leaves the sterilizer and is confirmed sterile, its sterility depends entirely on how it is stored and handled before use. A package does not become unsterile on a set calendar date simply because time passes. Instead, sterility is considered event-related: a package remains sterile until something happens to compromise it — moisture, physical damage, a dropped package, or improper handling. This principle, widely adopted in surgical technology practice and supported by AAMI ST79, shifts the focus from expiration dates to package integrity and storage conditions.

Event-Related Sterility

Event-related sterility means that the event, not the date, determines whether a package is still considered sterile. Events that compromise sterility include:

• Moisture or wet spots on the wrapper or pouch (moisture wicks microorganisms through packaging material)
• Tears, punctures, or open seals
• Dropping a package on the floor
• Prolonged exposure to dust, insects, or vermin
• Storage near HVAC vents, which creates turbulent airflow and condensation risk
• Improper temperature or humidity in the storage area

Because of this principle, every package must be inspected at the point of use, not just at the time it is placed on the shelf. If any event that could compromise integrity has occurred, the item is removed from service regardless of when it was sterilized.

AAMI ST79 Storage Guidelines

AAMI ST79 is the comprehensive guide for steam sterilization and sterility assurance in health care facilities. It establishes the following widely applied storage environment standards:

• Distance from floor: Packages must be stored at least 8–10 inches (approximately 20–25 cm) from the floor to protect against floor cleaning splatter, moisture, and traffic contamination.
• Distance from ceiling: Packages must be stored at least 18 inches (approximately 46 cm) below sprinkler heads to allow sprinkler activation and water dispersion in a fire. A general guideline is also to keep items away from the ceiling to reduce dust and heat accumulation.
• Distance from outside walls: Packages should be stored at least 2 inches (approximately 5 cm) from outside walls to prevent condensation from temperature differentials.
• Closed or solid shelving: Open wire shelving near HVAC ducts or in high-traffic areas increases contamination risk. Solid or semi-closed shelving is preferred.
• Temperature and humidity: The storage room should be maintained at controlled temperature (generally 64–75°F / 18–24°C) and relative humidity (generally 35–70%) per facility policy and AAMI guidance.
• Traffic control: Sterile storage areas should be limited-access, clean, and dry.

Package Integrity Inspection

Every package must be examined before it is brought to the surgical field. Inspect for:

1. Seal integrity — no open, lifted, or bubbling seals on peel pouches; no torn or unfolded edges on wrapped trays

2. Moisture — any wet spot or water stain is an automatic disqualifier

3. Tears or punctures — even a small corner tear breaks the microbial barrier

4. Color change indicators — chemical integrators or tape should show proper color change, confirming exposure to the sterilization cycle (note: a passed indicator does not confirm sterility, only that the item was processed)

5. Intact labeling — lot number, sterilizer number, and load number should be legible

If any of these findings indicate compromise, the package is removed from service, set aside for reprocessing, and documented on an inspection log. Never assume a package is fine because it looks mostly intact — any doubt removes it from use.

Sterile Transfer to the Surgical Field

Presenting a sterile item to the sterile field requires disciplined technique. Two common package types require different approaches:

Peel Pouch

Grasp the top corners of the pouch. Peel the two sides apart in a smooth, controlled motion, rolling the edges back and away from the contents. Hold the pouch away from your body and tilt it so the contents slide or fall directly onto the sterile field — or allow the scrub technologist to grasp the item. Do not reach across or over the sterile field. Do not flip the pouch downward in a way that drops debris or unsterile outer surface material onto the field.

Wrapped Tray

Loosen the outer indicator tape without tearing the wrap. Unfold the first flap away from you, then unfold the side flaps outward, and finally fold the near flap down toward you — never reaching over the open contents. Present the tray to the scrub technologist by holding the base of the tray steady, or set it at the edge of the back table with the flaps held fully open. The inner wrap, if used, is opened by the scrub technologist on the sterile field.

Key Safety Points

• When in doubt, throw it out. A compromised package endangers the patient through potential surgical site infection.
• The circulator never reaches over or touches the sterile field when presenting items.
• Items that fall to the floor or contact an unsterile surface are always considered contaminated.
• Sterile packages are never stored under sinks, near floor drains, or in areas subject to flooding.
• Document every removal-from-service decision on the inspection log — traceability is a patient safety requirement.

Mastering these principles protects every patient on your table and is a core competency tested by the NBSTSA CST examination.