Comparative interpretation and implications of updated points of ASHRAE’s position document on infectious aerosols

ASHRAE updates the position document on infectious aerosols in April 2020. This updated document is simplified by reducing the length of the background and the mechanism of virus transmission. On the basis of retaining most of the recommended measures from the previous version (2014 version), the new document introduces the evidence-level grading system to quantify the credibility of various measures, which has made it more operable and instructive. This paper summarizes the differences before and after the update chapter by chapter, and selects three aspects of the recommended measures from the new document, namely, the reserved design for the pandemic-era, ultraviolet sterilization, and personalized ventilation. This paper analyses the pros and cons of the measures, and provides the precautions for the application of the measures, which provides a reference for the engineers and researchers.