Poor outdoor air conditions from wildfires, which increasingly affect the western U.S., has been found to affect children’s respiratory health, but impacts vary depending on the types of ventilation systems at schools, according to Victoria McCrary, a Ph.D. student and graduate research assistant in the Sustainable, Healthy and Resilient Buildings Lab in the School of Civil and Construction Engineering at the College at Oregon State University.
Southern Oregon has seen more than 9,000 fire events this year compared to under 4,000 in other areas of Oregon, she said during the ASHRAE Annual Conference in Austin, Texas.
These events can have significant health impacts, she said. Each 10-microgram-per-square-meter increase in micrograms of particulate matter, or PM2.5, is associated with a 16% increase in mortality from ischaemic heart disease and a 14% increase in mortality from stroke, according to research published in the National Library of Medicine.
Because of the heightened impacts of wildfire smoke on children, it’s crucial for K-12 facility operators to use their ventilation systems in a way that protects occupants, McCrary said.
“We need to use buildings to help with the health and wellness of occupants when it comes to wildfires, and this is especially true when it comes to children,” said McCrary. “Children’s health is more at risk compared to adults … because their body weight to breathing ratio is so much higher than adults. They are more susceptible to particulate matter exposure, such that they experience bronchitis, heart disease and even early mortality.”
The Environmental Protection Agency provides a way to measure outdoor air quality through the Air Quality Index, or AQI, which measures the PM2.5 in the air.
While there is no official index for monitoring indoor PM2.5, “we notice that outdoor trends mirror indoors,” she said. She added that other sources may be affecting the indoor institutions, “such as cooking on a stove, or even the different ventilation types when it comes to filters,” she said. Although there is no official standard, the World Health Organization has a target threshold of 15 micrograms per meters cubed, meaning anything other that level would be considered good, healthy indoor air quality, she said.
As a result, this information is crucial to understanding, detecting and controlling exposure to particulate matter, “because we want to ensure that all … child-serving facilities such as schools are prepared in the long term when it comes to wildfire smoke.”
To determine how ventilation systems impact indoor PM2.5 concentrations, McCrary conducted a field study of three classrooms from April 2023 to July 2024. One classroom had a window AC and a portable air cleaning, another had a newer mechanical ventilation system and a staff room that had a mini-split HVAC unit and portable air unit, McCrary said during the season.
During two major wildfire events in August 2023, all three classrooms saw PM2.5 levels spike above WHO guideline levels for what is considered healthy for students, McCrary said. Levels were also higher prior to the peak, showing that even before the wildfire reached their area, there was smoke blowing in from other places that affected the classrooms.
During the month of August, the class without mechanical ventilation was unable to keep its median PM2.5 particulate concentrations below 10 micrograms per meters cubed. During the spike, when wildfire events most impacted the school, the mechanically ventilated room was able to keep PM2.5 concentrations much lower, “although still hazardous,” she said.
“Our preliminary results showed that mechanically ventilated rooms showed lower [indoor-outdoor PM2.5] ratios than that of non-mechanically ventilated rooms. Particulate matter concentrations were reduced if the room had mechanical ventilation … almost by half compared to outdoor concentrations,” McCrary said.
“Even though non-mechanically ventilated [rooms] showed lower concentration [compared with] outdoors, it still wasn’t as low as mechanically-ventilated rooms,” she said.
