Analysis: Most schools meet district ventilation standards. Experts say that may not be enough

With Philadelphia’s youngest students scheduled to return to school in a few weeks, the ventilation in most schools meets the district’s air circulation standards — but only because so few students are returning and the standard is minimal, a Chalkbeat analysis found. 

The air flow in about 94% of elementary schools is adequate by the district’s measures, according to hundreds of ventilation reports reviewed by Chalkbeat. But that is because fewer than 10% of the district’s enrolled students are returning and the district’s ventilation standards, which have long been acceptable for schools, are lower than that required to prevent the spread of airborne diseases.

Ensuring that the city’s aging buildings can be ventilated to help reduce the spread of the coronavirus has become one of the most urgent tasks facing district officials ahead of students returning to classrooms on Feb. 22. In recent months, many parents, teachers, and union officials have cited ventilation issues as a reason why schools couldn’t safely reopen for in-person learning. 

Declaring that it has “concerns” about ventilation in many schools, the Philadelphia Federation of Teachers requested the intervention of a third party through the city Department of Labor to determine whether it is safe to return. About 2,000 teachers for grades prekindergarten through second grade have been told to return Monday. But on Friday, Jerry Jordan, president of the PFT, told teachers not to come back to buildings because of safety concerns. He said they should continue to work remotely. 

Jerry Roseman, the union’s environmental scientist, said that simply looking at the numbers “is not good enough.” For instance, some of the schools may have mechanical ventilation systems that were shut down due to asbestos issues, and he said it isn’t always clear from the reports whether the issues have been resolved or if the school is relying on another ventilation method, such as window fans. 

“The reporting from the district needs to be more detailed to be able to make an independent assessment of safety,” he said. 

On ventilation, a binding agreement between the district and the union says the district must complete an “air balancer certification” for each space that will be occupied and identify the maximum occupancy based on “the available CFM or fresh air flow.” CFM stands for cubic feet per minute. The standard is 15 CFM per person.  

Experts on industrial hygiene explained that the standards, those sanctioned by The American Society of Heating, Refrigerating and Air-Conditioning Engineers, are meant only to maintain tolerable aesthetic conditions when people gather in a confined space. 

Chalkbeat’s analysis is based on the hundreds of “air balancing” reports available through the district’s Reopening Readiness Dashboard. Officials have now released reports for nearly all of the city’s 215 buildings, including 147 elementary schools to which students and staff are scheduled to return. Many schools have more than one report because the district commissioned a number of retests for schools that had poor ventilation numbers before any action was taken. 

In some schools, the district said it retooled neglected mechanical HVAC systems. There are three kinds of these: “housefan” systems in some of the oldest buildings, classroom unit ventilators, and central air handling systems. For up to 40 others officials decided to install window fans to recirculate air. 

Use of the window fans has been savaged on social media by parents and teachers who said the fans couldn’t protect students against the virus or keep kids comfortable in winter. Experts, however, told Chalkbeat the fans were a good strategy to improve ventilation.

National data indicates that schools aren’t major vectors for virus transmission in earlier grades. But it can be tough to curb transmission in regions with high rates of the coronavirus.

Philadelphia’s positivity rate was 6.3% as of Jan. 24, about one percentage point lower than when the district tried to reopen in November. The Pennsylvania Department of Education guidelines and the MOA with the teachers union say a hybrid model is acceptable if the city positivity rate is below 10%.

But with new variants of the coronavirus circulating, many are urging caution.

The district is also dealing with a legacy of distrust and past problems, such as temporarily closing schools to deal with loose asbestos and the botched construction project at Benjamin Franklin High School for the co-location with Science Leadership Academy. 

“The Hite administration has a track record of not putting health and safety of students and staff first,” said Charlie McGeehan, a member of Caucus of Working Educators and teacher at the U School. He said the fans being used in some schools “are the same as in my dorm room in college … this does not bring me to trusting the district.”

District officials, the Philadelphia Health Department and public health experts at Children’s Hospital of Philadelphia and the Centers for Disease Control and Prevention all support returning to in-person school for younger students.

Both Hite and district chief operating officer Reggie McNeil have described ventilation as an additional layer of protection to supplement wearing a mask, social distancing, and vigilant hygiene practices. But ventilation looms large in the public’s mind as crucial to safety.

Breaking down the analysis

Chalkbeat took a close look at the district’s ventilation reports to try to determine whether enough rooms were adequately ventilated compared to the number of students who chose hybrid learning. We found that all but 9 schools — 94% — meet the minimum accepted standard. 

We determined how many schools had enough adequately ventilated rooms for at least 10 occupants, and compared that number to the number of students who planned to return. We took into account that due to the cohorting system, only half the returning students would be in the building at the same time. 

The district’s ventilation reports use the 15 CFM per person standard to measure the safe occupancy of each room. Contractors also measured safe occupancy by social distancing standards, and the lower of the two numbers will be enforced.

Industrial hygienist David Krause said the ventilation standard is not remotely close to the air flow needed to curb the spread of a contagious virus. 

“The current code was never meant to control infections in non-healthcare settings. It was intended to … control body odor, nothing more,” Krause said.

Typically, ventilation for disease control is measured by air changes per hour, the rate at which outdoor air replaces indoor air, Krause said. The minimum ventilation that hospitals must have is 6 air changes per hour, and according to a Harvard study, schools should aim for 5 air changes per hour. 

Chalkbeat’s analysis indicates that the average city classroom with one of the district-installed fans has a rate of 2 to 2.5 air changes per hour. To reduce the probability of infection by about 90%, 6 air changes per hour are required; 2 air changes per hour reduces risk by less than 70%.

Still, the district’s ventilation numbers look better than they did several months ago. A Chalkbeat analysis from October found that only one-third of classrooms could safely hold 15 or more people. Since then, the district has ordered more than 1,000 fans to help remediate ventilation in its classrooms.

The fans, manufactured by Comfort Zone and Lasko, recirculate contaminated indoor air with outdoor air, and provide about 250 to 300 CFM of ventilation to any given room. Officials are aiming to have all the fans installed by Feb. 8, when staff return to schools, and McNeil said the work is now 37% complete. 

Hite mistakenly said during last Thursday’s school board meeting that each fan would be equipped with a gauge to measure temperature and CFM in real time, but later corrected himself.

While the fans are a good step, Krause said that ventilation measures should be supplemented with air filtration. 

Ventilation takes indoor air and replaces it with outdoor air, while the filters clean indoor air and spit it back out into the room. Both approaches add an extra layer of safety, but with filtration, students wouldn’t have to worry as much about cold air blowing into their classroom. It’s a more expensive approach than simply improving ventilation with window fans, but one that Krause says is affordable.

In New York City and Chicago, the school districts rushed to purchase air purifiers at the beginning of the school year, but Philadelphia didn’t. McNeil said that’s because most high-quality filters would damage mechanical ventilation systems in many of Philadelphia’s older school buildings. In place of installing filters, the district is looking at potentially adding portable air purifiers to some rooms with fans. 

Krause said he commends the district for testing and remediating antiquated ventilation systems, but questions the adequacy of the efforts to protect students and teachers. 

“What you’re doing is you’re peeling back the bandage on a wound in the United States that schools, the place we send our children, have not been a safe environment with respect to ventilation,” Krause said.

Dale Mezzacappa contributed to this report. 
Gabrielle LaMarr LeMee contributed data analysis.

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An earlier version of this story listed incorrect data for Watson Comly School and Overbrook Elementary School. Those schools have been updated.