Desks will stand 6 feet apart, surrounded by plastic shields, and their occupants will wear masks. But with students and teachers returning to classrooms across Long Island in the coming weeks, some fear COVID-19 could spread through the air in schools nevertheless.
Face-to-face contact and infected surfaces were quickly identified as culprits when the coronavirus began fanning out across the globe in the winter. More recently, however, public health experts have called attention to another, less-understood way the virus may infect: Tiny COVID-19-laced droplets seem capable of drifting well beyond 6 feet and of staying aloft for days.
In response, Long Island school districts are going beyond masks, social distancing and staggered schedules to safeguard the air in their facilities. Some districts are spending thousands of dollars on new air purifiers and top-to-bottom inspections of ventilation infrastructure. Other districts outlined less-ambitious ventilation plans in their reopening proposals, including simply keeping windows open and changing air filters regularly.
With much unknown about the virus' ability to infect while airborne, it is unclear how great a threat airborne transmission poses to children and teachers returning to classrooms. That adds yet another risk to reopening schools, but is a risk experts say is worth taking — with proper precautions in place.
“If you’ve got decent systems that are bringing fresh air into the building and have reasonable filtration, there may not be significant causes for concern,” said Corey Metzger, an engineer on the epidemic task force of the American Society of Heating, Refrigerating and Air-Conditioning Engineers, a national professional association. But “the reality is, there’s so much we don’t know, because the science is being developed right now.”
Airborne transmission of COVID-19 gained widespread attention in July, when 239 scientists released a letter imploring the medical community to acknowledge its threat.
“Hand-washing and social distancing are appropriate, but in our view, insufficient to provide protection from virus-carrying respiratory microdroplets released into the air by infected people,” the letter read. “This problem is especially acute in indoor or enclosed environments, particularly those that are crowded and have inadequate ventilation.”
Joseph Allen, a public health professor at Harvard University, was one of the signatories. In an interview, he said “viable virus” has been found in air samples taken 16 feet from an infected patient.
“But CDC and WHO have been slow to acknowledge this,” said Allen, referring to the U.S. Centers for Disease Control and Prevention and the World Health Organization and their positions on airborne transmission.
Gurumurthy Ramachandran, a public health professor at Johns Hopkins University, said tiny particles of the virus can remain suspended in the air for as long as 50 hours. But it is unclear how long aerosolized virus particles remain infectious, he said.
“Nobody really knows for sure,” he said.
Also unknown: how long the virus can survive while passing through ventilation equipment.
“We are not sure at this point about the ability of those airborne particles that have moved through a full system to be infectious when they get to another space,” Metzger said. “It’s entirely possible that they’re not, but we don’t know. The conservative approach is to make the assumption that they could be.”
Some Long Island districts aren’t taking any chances.
The Shelter Island district has spent around $10,000 on air purifiers for each classroom and office and on MERV 13 air filters. MERV, or Minimum Efficiency Reporting Value, is a scale that measures the strength of filters, with 1 being the weakest and 16 the strongest.
“The science is sort of a little unproven on the airborne stuff,” district Superintendent Brian Doelger said. “We want to be overly cautious.”
Alex Hochhausl, mechanical engineering manager at H2M architects + engineers, said eight Long Island districts have hired the firm in the past month to examine their heating, ventilation and air conditioning systems in search of vulnerabilities to the virus.
Franklin Square is one such district. In addition to hiring H2M, the district is upgrading filters and cleaning the ventilation machines in all 101 of its instructional spaces, in addition to requiring masks, separating desks and installing desk shields. The district said it paid H2M $7,500 for its work.
“Having all of these things in place is critical,” district Superintendent Jared Bloom said. “It’s not just one thing. It’s making sure that we’re doing everything that we can.”
Other districts reported less-thorough interventions into their ventilation systems in reopening plans. Some pledged little more than to open windows whenever possible and to change filters frequently.
Ramachandran noted that improving those systems might be too expensive for some school districts, as many already struggle to provide good indoor air quality.
New York City also is working to keep the virus out of the air in its schools. The city's Department of Education has purchased more than 10,000 portable air filters, and teams of engineers and ventilation experts are inspecting classrooms, bathrooms and other facilities to assess air quality and flow.
State reopening guidelines said relatively little about ventilation. The Health Department called on increasing “ventilation with outdoor air to the greatest extent possible.” The Education Department said schools should “meet or exceed ventilation requirements” and consider consulting design professionals and installing higher grade filters.
Hochhausl called the guidance “very vague.”
In June, Gov. Andrew M. Cuomo said health officials believe air conditioning systems may be circulating the virus through restaurants and other businesses. The state has required malls and gyms to be outfitted with high-grade filters before reopening.
Cuomo's office did not respond to a question about why the state did not require the same in schools.
Health Department spokeswoman Erin Silk said schools pose different risks and challenges than gyms and malls "given their varied building design and configuration."
That is why, Silk said, "We’re telling schools they need to use whatever methods they can — windows, outside classes, HVAC systems — to make sure kids, teachers and staff are safe."
The Education Department did not respond to a question about the limited discussion of ventilation in its reopening guidelines.
Public health experts and mechanical engineers outlined a range of steps school districts could take to mitigate the risk of airborne transmission of the virus.
First, schools should ensure their mechanical ventilation systems are operating as designed, Metzger said.
Second, schools should maximize the new air cycling indoors to flush out old, potentially contaminated air. Opening windows could help for part of the year, but not when it’s blisteringly hot or cold, Metzger said. Increasing the outdoor air mixing into mechanical ventilation systems, or even simply setting up fans to move air through classrooms, might serve as all-weather solutions.
Third, districts should seek to clean the air passing through their ventilation systems. Metzger recommended filters with a MERV rating of at least 13. He said filters typically used in schools fall in the 6 to 8 range.
But Hochhausl said it may be hard to upgrade filters in many schools with ventilation systems that were built decades ago and were not designed to provide high-level filtration.
“The schools were intended to be schools, not hospitals,” he said.
If filter upgrades are not possible, portable air purifiers, such as those purchased on Shelter Island, are an alternative.
Ultimately, however, public health and engineering experts said retrofitting ventilation systems should be a second-order concern to other fronts in the fight against the coronavirus. Those include wearing a mask, keeping a safe distance from others, washing hands frequently, keeping kids home when they're sick and switching to remote learning when infections in the region are increasing.
With such measures in place, a return to schools is likely worth it, said Linsey Marr, an engineering professor at Virginia Tech.
“If the classrooms weren't too crowded and if masks were mandatory at all times, covering the nose and mouth, and if community transmission were low like in New York, I think the benefits would outweigh the risks,” she said.