A box fan, an air filter — and duct tape to attach them.
With four such cobbled together devices, at perhaps a total of $150, the vice-presidential debate on Wednesday night could be made much safer, according to experts in airborne viruses.
Vice President Mike Pence and Senator Kamala Harris will be seated more than 12 feet apart on the podium, with plexiglass barriers between them. Mr. Pence and his aides had objected to the barriers, but relented on Tuesday night.
The barriers might make more sense if Mr. Pence and Ms. Harris were seated more closely together on the podium, scientists said. But the risk in this setting is airborne transmission of the coronavirus, and the barriers will do nothing to protect Ms. Harris and the moderator, Susan Page, Washington bureau chief of USA Today, if Mr. Pence were infected.
On Monday, the Centers for Disease Control and Prevention released new guidelines confirming that the virus can be carried aloft by aerosols — tiny droplets — farther than six feet indoors. In one recent study, scientists isolated infectious virus some 16 feet from an infected patient in a hospital.
Linsey Marr, an expert on airborne viruses at Virginia Tech in Blacksburg, Va., laughed outright when she saw a picture of the debate setup. “It’s absurd,” she said.
When she first heard there would be plexiglass barriers, Dr. Marr said, she had imagined an enclosure with an open back or top: “But these are even smaller and less adequate than I imagined.”
Other experts said the barriers might have made some sense if the debaters were to be seated close together.
“Those plexiglass barriers are really only going to be effective if the vice president or Kamala Harris are spitting at each other,” said Ellie Murray, an epidemiologist at Boston University. “Those are really just splatter shields.”
The C.D.C. on Tuesday cleared Mr. Pence for the debate, saying he had not been in close contact with anyone known to be infected. The agency’s definition of close contact is being within six feet of an infected person for at least 15 minutes.
Yet Mr. Pence said at a rally on Tuesday evening that he had met with President Trump, who last week tested positive for the coronavirus, that morning in the Oval Office.
“What we’ve been seeing over the past week is that there are a lot of spaces in the White House that are pretty enclosed, pretty poorly ventilated, where people can come into close contact even if they are more than six feet away,” Dr. Murray said.
“I would be very surprised if he has not been close enough to some of these people to at least potentially have been infected.”
Mr. Pence has cited multiple negative tests as proof that he is not infected. But tests for the coronavirus may not yield positive results for up to 14 days after exposure to the virus.
Given the risk that Mr. Pence may be infected, experts said, the Commission for Presidential Debates should focus instead on preventing airborne transmission of the virus by improving ventilation in the debate venue.
“The point is that at 12 feet 3 inches apart, spray droplet transmission is not the issue,” said Donald Milton, an aerosol expert at the University of Maryland. “What is the ventilation like? What is the direction of the airflow?”
Scientists have expressed similar concerns about former Vice President Joseph R. Biden Jr. At the presidential debate on Sept. 29, Mr. Trump may have been at the peak of his infectiousness — which studies have shown begins somewhere around two days before symptoms appear.
At that debate, the two lecterns were about 12 feet apart. Mr. Biden’s campaign has said the debate did not meet the C.D.C. requirement for close contact.
But in a press statement accompanying the new guidance this week, the C.D.C. said, “People are more likely to become infected the longer and closer they are to a person with Covid-19.”
The presidential debate was 90 minutes and Mr. Trump talked loudly during much of it, which can release 10 times as much aerosolized virus as breathing alone, experts have found.
The debate was held in a large hall, but the hosts, the Cleveland Clinic, have not disclosed ventilation arrangements for the space.
“From what we saw last week at the debates, there were very few, if any, controls in place, including what looks like the failure of the president to take a test that morning,” said Joseph Allen, ventilation expert at the Harvard T.H. Chan School of Public Health. “It’s just shocking.”
Of the plexiglass setup for the vice-presidential debate, Dr. Allen said: “My biggest concern is that millions of people will be getting the message that this is what an effective set of controls looks like.”
Dr. Milton and his colleagues have contacted the debate commission, as well as both campaigns, to recommend purchasing plug-and-play air filters — excellent models cost just $300 each — or four box fans and air filters taped together. Each debater would have one device positioned to suck up and clean the air exhaled, and another to produce clean air.
In research conducted with singers over the past few months, Jelena Srebric, a mechanical engineer at the University of Maryland, found that this so-called Corsi box — named for Richard Corsi, an air quality expert at Portland State University — can significantly decrease the number of aerosols.
Another solution, experts said, is simply to move the debate online. “I don’t understand the resistance to a virtual format,” said Natalie Dean, an epidemiologist at the University of Florida.
“We have moved much of our lives online. The technology is there. Why the insistence on an in-person debate?”
A remote debate would protect Ms. Harris if Mr. Pence were infected — and the format would keep Mr. Pence safely cloistered from others who could be infected.
“Given that the president is currently sick with what is a deadly disease, the vice president should be being protected,” Dr. Murray said. “I think it makes sense to be taking extra precautions to not end up in a situation where both the president and the vice president could be sick at the same time.”