What suburban Portland school districts say about their ventilation rates

Eight of the 12 largest school districts in the Portland area say they’ve met or surpassed minimum recommendations for ventilation in all classrooms.

Beaverton, Centennial, Hillsboro, Lake Oswego, Oregon City, Reynolds, Tigard-Tualatin and West Linn-Wilsonville all say they’ve achieved or exceeded bare minimum recommendations from the Harvard TH Chan School of Public Health of at least three to four air changes per hour.

Meanwhile, four other districts – Portland, David Douglas, Gresham-Barlow and North Clackamas – haven’t reached that threshold or didn’t provide The Oregonian / OregonLive with data or answers stating that they have.

Studies show the risk of transmitting COVID-19 or other airborne diseases grows considerably when a room’s total volume of air is not frequently replaced with fresh or filtered air every hour.

A bevy of experts and organizations told The Oregonian / OregonLive that districts should not settle for the minimum – and should instead target at least five or six air changes per hour.

Beaverton says it has reached at least five in every classroom. Hillsboro and Oregon City say they’ve attained at least six.

But while some districts didn’t explain their methodology, others said they calculated their classroom rates by using averages rather than checking each room. That means officials determined the overall air-handling capacity of their ventilation systems each hour, then divided that by the total volume of air in spaces served by those ventilation systems.

Experts say that’s an acceptable practice, if done with care and precision. Like in other districts, Hillsboro’s Operations Officer Casey Waletich said he’s confident his district’s numbers are accurate, with the district even hiring an engineer to double-check its airflow equations.

Only Portland, David Douglas and Oregon City say they hired consultants who went to classroom to classroom to measure air changes.

Elliott Gall, an associate professor at Portland State University who specializes in indoor air quality, said he believes calculating air changes by room is most accurate because of complicated ventilation systems that can involve a “rat’s nest” of duct work that distributes air unequally between spaces. .

“I think they deserve credit,” Gall said of the districts that measured airflow in each individual room.

Oregon City did not post airflow results on its website or keep written records of its numbers, said Director of Operations Michael Sweeten. But Sweeten said the district is confident all classrooms have achieved at least six changes per hour.

Both Portland’s and David Douglas’ websites include school-by-school reports outlining airflow in each classroom, cafeteria and gym.

Fully 25% of elementary and middle school classrooms in Portland Public Schools didn’t meet experts’ bare minimum recommendation of at least three hourly air changes, with portable air purifiers running. In the high schools, it was less than 1%.

In David Douglas, 7% of classrooms in elementary and middle schools and 6% in high schools did not meet the minimum of three air changes. But that was before the district placed powerful air purifiers in every classroom – meaning the results look even better when compared to Portland’s. David Douglas plans to take measurements again at a date that hasn’t yet been set.

Experts say broadly distributing room-by-room numbers can create public-relations headaches – if the results are bad.

“In many places, they do not want to make this information public,” said Jose-Luis Jimenez, an atmospheric chemistry professor at the University of Colorado Boulder and expert in indoor COVID-19 transmission. “The last thing you want is for people to know the ventilation is not good.”

– Aimee Green; [email protected]; @o_aimee

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