Effect of Poor Outdoor Air Quality and HVAC Settings on Indoor Air Quality on the University of Utah Campus

TRISTALEE MANGIN, Kerry Kelly, Darrah Sleeth, Dillon Tang, Zachary Palmer, Zachary Barrett, Sean Nielson, University of Utah

     Abstract Number: 520
     Working Group: Indoor Aerosols

Abstract
Individuals spend up to 90% of their time indoors, and poor indoor air quality (IAQ) is associated with numerous adverse human health effects. Yet, it has been less frequently studied than outdoor air quality. Particulate matter (PM), specifically PM2.5 concentrations, is a key driver of adverse health effects. This study aims to understand the impact of pollution episodes (wildfire smoke, dust events, and temperature inversions) on indoor air quality using a network of low-cost air quality sensors on a university campus and to identify the effect of HVAC operations on IAQ.

This study deployed 21 low-cost air quality sensor nodes measuring PM2.5 and carbon dioxide (CO2) levels, with 17 sensors at indoor locations and four sensors at two outdoor locations across the University of Utah campus. We developed a dashboard to share the AQ measurements in real time with facilities management. The sensors were deployed in November 2022 and continue to operate. We identified the following outdoor pollution events: four temperature inversion events (when the valley heat deficit values exceeded 4.04 MJ/m2 for three or more days), 10 dust events (when the regulatory PM10 concentrations exceeded 100 ug/m3 with a wind speed greater than 5 m/s), and two wildfire smoke events (using the aerosol optical depth results from NASA WorldView satellite images). The University of Utah facilities management has provided access to the HVAC settings and equipment measurements for these pollution episodes.

Wildfire smoke has the largest impact on IAQ of the three pollution events studied. These events had the highest indoor-to-outdoor PM2.5 correlation with an R2 value of 0.68, while inversion and dust events had indoor-to-outdoor correlation values of 0.32 and 0.44, respectively. The wildfire smoke events resulted in the highest hourly average PM2.5 concentrations for 12 of the 17 indoor locations compared to inversion and dust events. During the wildfire events, 9 locations exceeded World Health Organization 24-hour PM2.5 concentration guidelines for a total of 13 days, with a maximum hourly PM2.5 concentration of 37.4 ug/m3. This is a surprising finding, given that many of the buildings are equipped with MERV13 filters, which have an efficiency rating of >50% for PM ranging from 0.3 – 1 um and >85% for PM ranging from 1 – 3 um, both of which are associated with wildfire events. Preliminary HVAC analysis indicates that HVAC operations impact IAQ during pollution events. For example, the team found one location where an open outdoor damper resulted in an increase in the indoor-to-outdoor PM2.5 concentration ratio from 0.33 to 0.79. Further analysis of HVAC operations is underway for the additional locations and different pollution events.