Approximately 1,261 of Hawaii’s 12,000 public school classrooms have limited access to fresh air from outside because they rely on air conditioning, and 377 of those classrooms were found by a contractor to have concerning levels of carbon dioxide — a sign of poor air ventilation, which is a risk factor for the spread of COVID-19.

With tens of thousands of students back to school this week, and masking now optional both indoors and outdoors in the public schools, the role of inadequate classroom ventilation in COVID-19 contagion is widely seen as a more urgent issue than ever.

“My worry is that with unmasking, we’re all sort of holding our breath with what’s going to happen with infection rates,” said Andrea Eshelman, deputy executive director of the Hawaii State Teachers Association, the union that represents 13,700 public schools teachers statewide.

Added Dr. Scott Miscovich, whose Premier Medical Group has served as a consultant on classroom air quality in three other states, “This should have been taken care of a year ago when our children (in Hawaii) went back to school. It certainly should’ve been done before our children returned to school (Monday), for safety.”

Board of Education member Lynn Fallin, the new head of the board’s Finance and Infrastructure Committee, said while it is not clear whether the department has since fixed ventilation in all the classrooms with high carbon dioxide levels, “I don’t want the headline to say all the schools are not safe. That would not be accurate.” She said she believes the DOE has made ventilation a high priority, and its ongoing work on the issue has constituted “a thorough job during a rough period of time.”

The results of classroom ventilation assessments and other steps by the DOE to improve classroom air quality are outlined in a July 26 letter to Eshelman from Randall M. Tanaka, assistant superintendent for the DOE Office of Facilities and Operations.

Eshelman, in an interview with the Honolulu Star- Advertiser, said that the letter marks the first time the DOE has responded with significant details to a formal request for information that the teachers union made almost a year ago, in September. The union had followed up with additional requests in their monthly meetings with DOE but has been frustrated at receiving no major responses until now, and Eshelman said the letter still doesn’t answer many of the union’s questions.

The DOE did not immediately respond to an email query Monday from the Star-Advertiser.

In the letter, Tanaka describes the classroom carbon dioxide assessments among the department’s “steps to improve air quality to reduce the risk of airborne spread of COVID-19.”

Of the state’s 12,000 public school classrooms, 10% have central air conditioning or “large packaged air conditioners.” Approximately 1,261 classrooms have “limited access to outside air due to central air conditioning,” Tanaka said. The letter does not say where those classrooms are.

Starting in September, he said, the DOE used a contractor “to assess the carbon dioxide levels in classrooms identified as potentially having compromised ventilation,” and 335 classrooms were equipped with sensors feeding real-time data to the contractor. Carbon dioxide readings were collected during operational hours between 6 a.m. and 6 p.m., excluding weekends, holidays and intersessions.

The carbon dioxide levels “infer the probability of breathing in another’s exhalation,” and the higher the levels, the greater the probability, Tanaka said.

The average of the highest 5% of all carbon dioxide readings determined where a classroom fell in one of five tiers, which “prioritizes the classrooms that warrant further actions to increase ventilation,” Tanaka said.

The data collected from the 335 classrooms “informed the estimated carbon dioxide for 904 of the remaining classrooms; estimates were based on similar room configurations and air conditioning supply,” Tanaka said.

Using that system of extrapolation, 862 classrooms fell into tiers 1 and 2, which had less than 1,100 parts per million of carbon dioxide (see accompanying chart). Another 377 classrooms fell into tiers 3, 4 and 5, with carbon dioxide levels above the threshold of 1,100 parts per million. Three of those classrooms were in tier 5, with more than 2,000 parts per million. The letter did not address another 22 classrooms that have limited fresh air because of air conditioning.

“The Office of Facilities and Operations will follow up on the classrooms identified in tiers 3, 4 and 5 to ensure steps are being taken to improve air quality to the extent possible,” Tanaka said in the letter, but he did not provide details on those steps or say where the assessed classrooms are.

Fallin said that in a meeting last week with Tanaka, she learned that the DOE planned to “review” the 73 classrooms in tiers 4 and 5 before school started. She said the board will check to see whether those classrooms with the most severe carbon dioxide problems were addressed. She also noted that guidelines for the schools to ensure adequate air circulation are being strengthened.

Tanaka said in the letter that the DOE has worked on additional multiple fronts to improve air quality in classrooms. For instance, he said, 20-inch box fans were purchased and distributed “for every classroom throughout the department” prior to school year 2021-22. More than 4,000 HEPA air cleaners also were purchased for the schools, for use especially in classrooms that lack doors or windows that open to the outside.

Schools also were given supplies to build their own Corsi-Rosenthal air cleaners, using MERV-13 filters and box fans, he said. Six hundred carbon dioxide sensors were purchased and distributed so schools could monitor their own levels. “Central air conditioners are maintained regularly to ensure optimal air flow,” Tanaka said.

Miscovich, who reviewed the letter at the request of the Star-Advertiser, said he’s encouraged that the DOE has taken some steps toward better air quality, but it’s not enough.

“Tier 3 and above would not be where I want my children,” he said.

He said every classroom must be assessed individually. The standard for a classroom is six “air changes” an hour, in which six times the volume of air in a classroom moves through high-quality HEPA filtration, Miscovich said. “You don’t just hand someone a fan and say, ‘Ventilate your classroom.’ There’s a science behind this.”

Infectious disease expert Tim Brown of the East-West Center, who spoke Monday on the Star-Advertiser’s “Spotlight Hawaii” livestream program, said the risk of transmission now in the schools is significant. “With schools opening, that’s a real concern because children in schools without masks will transmit (the COVID-19 variant) BA.5. There’s virtually no question of that,” Brown said. “And they will then take it home, and that will give it entry into our multigenerational households here in Hawaii. The people at the greatest risk with any COVID right now are the elderly.”