Sterility: Event/Date Related?

How long can sterile packs and trays be stored and still remain sterile?

This is a frequently asked question in CS, SPD and OR departments. Regretfully, organizations such as the Centers for Disease Control and Prevention (CDC), the FDA, AORN, AAMI and The Joint Commission (TJC) do not provide uniform answers to this important question.

Currently, it is left up to each individual healthcare facility to determine their sterile shelf-life protocols regarding sterile packs and trays. More importantly, each individual facility must decide if the sterility of their packs and trays are ‘event’ related or ‘date’ related.

When it comes to shelf-life protocols, most facilities subscribe to ‘event’ related which means they recognize that sterile packs and trays are ‘sterile’ until an event occurs that compromises the sterility of the pack or tray. Those facilities that subscribe to ‘date’ related use an arbitrary date (i.e., 30 days) to determine when a pack or tray is no longer considered sterile and must be reprocessed. Regardless of the protocol chosen, the healthcare facility must clearly spell out the practices that the facility will follow relating to the sterility status of their packs and trays, or risk a possible citation by TJC.

The debate as to which method is better goes back over a long period of time. “Studies in the early 1970s suggested that wrapped surgical packs and trays remained sterile for varying periods depending on the type of material used to wrap the trays. Safe storage times for sterile packs vary with the porosity of the wrapper and storage conditions (e.g., open versus closed cabinets). Heat-sealed, plastic peel-down pouches and wrapped packs sealed in 3-mil (3/1000 inch) polyethylene overwrap have been reported to be sterile for as long as 9 months after sterilization.”1

A number of years ago a hospital was doing some renovations. Behind a bricked-in wall they found a small storage area that had been sealed off since 1927. Sitting on the shelves were dozens of instrument trays wrapped in paper. The infection control manager tested the trays and found that the instruments were still sterile after 70+ years of sitting on the shelf. 2 This is an excellent example of sterility being ‘event’ related and not ‘time’ related.

In 1983 the CDC published recommended storage times for various sterile packs. “Supplies wrapped in double-thickness muslin comprising four layers, or equivalent, remain sterile for at least 30 days. Any item that has been sterilized should not be used after the expiration date has been exceeded or if the sterilized package is wet, torn, or punctured.” 3

These old recommendations from the CDC are still being followed by some healthcare facilities; however, the CDC’s recommended shelf-lives are considered too short by most healthcare facilities. Their reason for rejecting the CDC’s recommendations is that a lot of valuable labor, expensive supplies, resources and time are wasted by reprocessing perfectly good sterile packs and trays. Their position is further supported by recent modifications to TJC’s Accreditation Standards that reflect their belief that sterility is ‘event’ related and not ‘time’ related.

The majority of U.S. healthcare facilities utilize the concept that sterilized packs and trays have an ‘event’ related shelf-life. Under this widely accepted concept, it is acknowledged that sterile packs and trays have an indefinite shelf-life and will remain sterile, unless they become contaminated due to an external event (i.e., torn or wet packaging). This concept has been supported by numerous organizations, studies and papers over the years.

In looking at AAMI ST79 we see that “The shelf life of a packaged sterile item is event-related and depends on the quality of the packaging 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 how it is indicated on the product.” 4

And from the AORN we read that “The shelf life of a packaged sterile item should be considered event-related. [1: Strong Evidence] The sterility of an item does not change with the passage of time, but may be affected by particular events (e.g., amount of handling) or environmental conditions (e.g., humidity).” 5

All sterile packaging systems (rigid containers, wraps etc.) are required under FDA 510(k) clearance regulations to have a shelf-life stated and then tested to that shelf-life if they are a terminal sterilization packaging system. 6  A majority of sterile packaging systems have at a minimum a six month shelf-life and most have a one year shelf-life. However, this is only a factor if you are not an event related facility. If you are an event related facility, you don’t have to recognize the stated shelf-lives of packaging systems as they are noted in the manufacturer’s IFU.

Every healthcare facility should have an established, written policy so that the shelf-life of packaged sterile items is addressed on the basis of handling, the conditions during transport, the quality and type of the wrapped material along with the storage conditions. Care needs to be taken during the processing of sterile packs and trays so that contamination of the packs can and will be avoided during storage. After storage and before transport to surgery, the packs and trays must be inspected for dryness and integrity to ensure the sterility of the contents.

  1. Maloney JM, Kohut RD. Infection control, barrier protection and the treatment environment. Dent. Hyg. (Chic). 1987; 61:310-3.
  2. Mayworm D. Sterile shelf life and expiration dating. J. Hosp. Supply, Process. Distri. 1984; 2:32-5
  4. ANSI/AAMI ST79 2010 & A1:2010 & A2:2011 & A3:2012 & A4:2013, 8.9.3, page 88
  5. AORN Guidelines for Perioperative Practice, 2017, Guidelines for Selection and Use of Packaging System for Sterilization, Recommendations III. D., page 854