This document provides a summary of international guidelines on reusing and reprocessing single-use masks and respirators. While generally not recommended, some guidance supports extended use or reuse as a last resort during shortages. Comparisons show limited evidence and inconsistencies, especially around respirator reuse involving aerosol procedures. The document provides references on methods for cleaning and reusing N95 masks that have been proposed. It questions whether mask reuse is worth the costs, benefits, and risks.