The sterile field should be covered if it will not be immediately used or during periods of increased activity. - AORN 2019 AORN Guideline for Sterile Technique. In: Guidelines for Perioperative Practice. Denver, CO: AORN, Inc. 2019: electronic release. Sterile-Z is a registered trademark of TIDI Products, LLC. ©TIDI PRODUCTS, LLC. ALL RIGHTS RESERVED. Untitled-2 1 1/7/2019 9:02:38 AM