Measured Influence of Overhead HVAC on Exposure to Airborne Contaminants from Simulated Speaking in a Meeting and a Classroom

Measured Influence of Overhead HVAC on Exposure to Airborne Contaminants from Simulated Speaking in a Meeting and a Classroom

TitleMeasured Influence of Overhead HVAC on Exposure to Airborne Contaminants from Simulated Speaking in a Meeting and a Classroom
Publication TypeJournal Article
Year of Publication2021
AuthorsBrett C Singer, Haoran Zhao, Chelsea V Preble, William W Delp, Jovan Pantelic, Michael D Sohn, Thomas W Kirchstetter
JournalIndoor Air
Date Published09/2021
KeywordsCOVID-19, Expired bioeffluents, FLEXLAB, Respiratory aerosols, ventilation effectiveness
Abstract

Tracer gas experiments were conducted in a 158 m3 room with overhead supply diffusers to study dispersion of contaminants from simulated speaking in physically-distanced meeting and classroom configurations. The room was contained within a 237 m3 cell with open plenum return to the HVAC system. Heated manikins at desks and a researcher operating the tracer release apparatus presented 8–9 thermal plumes. Experiments were conducted under conditions of no forced air and neutral, cooled, or heated air supplied at 980–1100 cmh, and with/out 20% outdoor air. CO2 was released at the head of one manikin in each experiment to simulate small (<5 μm diameter) respiratory aerosols. The metric of Exposure Relative to perfectly-Mixed (ERM) is introduced to quantify impacts, based on measurements at manikin heads and at three heights in the center and corners of the room. Chilled or neutral supply air provided good mixing with ERMs close to one. Thermal stratification during heating produced higher ERMs at most manikins: 25% were ≥2.5 and the highest were >5× perfectly mixed conditions. Operation of two within-zone air cleaners together moving ≥400 cmh vertically in the room provided enough mixing to mitigate elevated exposure variations.

URLhttps://onlinelibrary.wiley.com/doi/10.1111/ina.12917
DOI10.1111/ina.12917
Refereed DesignationDoes Not Apply