- Open trays placed on countertops are considered inappropriate because they expose sterilized instruments to environmental contamination, such as dust, moisture, and airborne microorganisms.
- This exposure compromises the sterility of the instruments, increasing the risk of infection.
- In contrast, sealed sterile pouches, covered trays, and sterile packages stored in clean environments maintain a protective barrier, preserving sterility until use.

Reference: Spaulding HT, "Principles and Practice of Sterilization," Volume 1, Chapter 3, p. 45