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URMC / Sterile & Materials Processing Department / Event-Related Sterility

Event-Related Sterility


Event-Related Sterility Maintenance Policy defines procedures intended to maintain the sterility of packages until they are used. This document focuses on event-related sterility maintenance of hospital-prepared packages containing sterile supplies wrapped in single-use or reusable materials. Since some supplies have expiration dates and degrade over time, this document covers only those supplies for which the manufacturer or the distributor does not provide expiration dating in the form of labeling, instructions of use, or other statements.

For years, the subject of expiration dating has generated considerable debate. Many hospitals have considered 30 days to be the standard time period for dating hospital wrapped sterile supplies, principally because of 1971 (1) and 1973 (2) shelf-life studies conducted by the Center for Disease Control. Those results indicated that items double-wrapped in muslin had a shelf life of three weeks, and that packs stored in dust covers were considered sterile for at least nine months. Recent studies suggest that current standards for sterility testing can be improved by the addition of event-related testing, and that contamination of wrapped trays may occur within days, instead of weeks (3).  New and improved packaging materials, along with greater understanding of the factors affecting sterility, have fueled the debate over expiration dating. Changes in JCAHO Accreditation Standards reflect the premise that contamination is "event-related" and not "time-related", and recognize the hospital's expertise in maintaining and delivering sterile products.

While the new standard provides new freedom, it also puts new responsibility on the hospital professional. The major difference in the new standard is that a specific date is no longer required. Hospitals must now establish written policies based on their unique internal practices. The impact of this can be substantial, representing savings in both reprocessing and labor costs. The timely and costly practice of reprocessing is greatly reduced and staff is free to spend time in more productive job functions (i.e., pack preparation, not pack reprocessing).

With the change in accreditation standards, hospitals are now able to develop procedures that more accurately reflect their sterile containment needs.


Rationale for changing to an Event-Related Sterility Maintenance Policy

  • Patient-care items purchased from manufacturers as sterile typically use "event-related" labels (4) such as "Sterile unless the package is opened or damaged".
  • The following professional organizations recommend practices that do not require time-related expiration dating:
    • AAMI Draft, 1993 (5)
      • Shelf-Life: "The shelf-life of a packaged sterile item is event-related and depends on the quality of the wrapper material, the storage conditions, the conditions during transport, and the amount of handling. There should be written policies and procedures for how shelf-life is determined and for how it is indicated on the product."
      • Expiration Dating: "Each item intended for use as a sterile product must be labeled with a lot control number, a control date for stock rotation, and the following statement: 'Product is not sterile if packaging is open, damaged, or wet. Please check before using.'"
    • JCAHO (6) "There are written policies for the shelf-life of all stored items." IC.5.1.2
    • AORN, Recommended Practice VIII (7) "Shelf-life of a packaged sterile item is event-related,..."
  • Cost of reprocessing items due to Expiration dates vs. Actual compromise of package sterility.


  • Define goals for the policy.
  • Develop proposal for Infection Control Committee
  • Develop a cost benefit analysis
    1. Cost of sterilization materials
    2. Time spent repackaging
    3. Staff salary costs
    4. Anticipated annual savings
  • Review technical documentation on barrier quality of packaging materials.
  • Review current practices to establish compliance with:
    1. Local and state laws - consult your hospital’s Infection Control and Risk Management departments.
    2. AAMI
    3. AORN
    4. JCAHO
    5. CDC
  • Develop and implement initial and on-going quality assurance testing protocol.
  • Develop a policy:
    1. Define labeling policy
    2. Define events that would require reprocessing of packages
    3. Determine which items need to be dated
    4. Determine rotation policy
    5. Define how to monitor compliance
  • Develop and implement training programs.
  • Monitor infection rates before and after implementation of new policy. Document other changes in hospital practices that could impact infection rates to be able to identify the potential cause of a change in infection rates.

Factors Affecting Sterility

Barrier Efficiency of Packaging Material—Visual Evidence of Compromise Packages

  • Tears
  • Holes
  • Rupture of Seals and Closures
  • Wetness
  • Crushed Packages

Storage conditions

  • Microbial Contamination of the environment
  • Air Movement
  • Traffic
  • Location
  • Temperature
  • Humidity

Handling, and Transport

  • Dropping
  • Compression

Opening the package

Standard Requirements

OLD STANDARD REQUIRED: "Designation of the shelf-life for each hospital-wrapped and hospital-sterilized medical item, and to the maximum degree possible for each commercially prepared item by a specific expiration date that sets a limit on the number of days an item will be considered safe for use." (JCAHO Accreditation Manual, IC.5.1.4, 1989)

NEW STANDARD REQUIRES: "Written policies for addressing the shelf-life of all stored sterile items." (JCAHO Accreditation Manual, Standard 5:5.1.2, 1990.)


  1. Standard, P. G., Mackel, D. C., Mallison, G. F., "Microbial Penetration Of Muslin- and Paper-Wrapped Sterile Packs Stored on Open Shelves and in Closed Cabinets." Applied Microbiology, Vol. 22, No. 3, pp. 432-437, 1971.
  2. Standard, P. G., Mackel, D. C., Mallison, G. F., "Microbial Penetration Through Three Types of Doublewrappers of Sterile Packs." Applied Microbiology, Vol. 26, No. 1, pp. 59-62, 1973.
  3. Widmer, A. F., Houston, A., Bollinger, E., Wenzel, R., "A New Standard for Sterility Testing for Autoclaved Surgical Trays." Journal of Hospital Infection, Vol. 21, pp. 253-260, 1992.
  4. Mayworm, D., "Sterile Shelf-Life and Expiration Dating.", Journal of Hospital Supply, Processing and Distribution, Vol. 2, No. 6., pp. 32-35, 1984.
  5. Association for the Advancement of Medical Instrumentation, "Draft: Good Hospital Practice: Steam sterilization and sterility assurance.", ANSI/AAMI ST46, 1993.
  6. Joint Commission on Accreditation of Healthcare Organizations, Accreditation Manual For Hospitals, Chicago: JCAHO, 1993.
  7. Association of Operating Room Nurses, "Recommended Practices for Selection and Use of Packaging Systems." AORN Journal, Vol. 56, No. 6, pp. 1096-1100, 1992.