Investigating the Particulate Matter and CO2 Relationship During Wildfire and Prescribed Burn Smoke Events

C. VICTORIA MCCRARY, Sara Jones, Perry Hystad, Molly Kile, Parichehr Salimifard, Oregon State University

     Abstract Number: 236
     Working Group: Indoor Aerosols

Abstract
Wildfire smoke is detrimental to occupant health. Ventilation and air cleaning can help maintain and improve indoor air quality (IAQ). Carbon dioxide (CO₂) is used as an IAQ proxy for occupancy and ventilation rate, with CO₂ monitoring employed for ventilation control. This practice implies that PM could be controlled by maintaining CO₂ levels. However, it is unclear whether the relationship between CO₂ and PM is consistently correlated. Therefore, we used linear regression to assess the validity of using CO₂ as a reliable proxy for PM using data collected at a preschool located in Southern Oregon that experiences frequent wildfire smoke events. PM (μg/m³) and CO₂ (ppm) were measured using collocated low-cost (PurpleAir PA-I and PA-II) and mid-cost (IC Sentinel) sensors. We placed these sensor pairs in three different rooms at the preschool: a classroom with a window air conditioning unit, a classroom with mechanical ventilation, and a staff room with a mini-split and heat recovery ventilation. We selected consecutive workdays that captured comparable occupancy and scheduling before, during, and after smoke events. Preliminary results indicated that PM concentrations varied significantly between wildfire smoke and non-wildfire smoke days. CO₂ concentrations notably fluctuated between days and rooms. The interaction between PM and CO₂ displayed different patterns each day, with smoke days exhibiting a more consistent pattern than non-smoke days. We intend to conduct additional analysis that examines different PM size ranges to explore how the particle size fraction is affected by the PM and CO₂ relationship, explore different mechanical ventilation types across schools, and quantify the correlations using statistical analysis.