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A five-level strategy to make returning to the office safer

“When the time is right," Joseph Allen said, "these are the strategies we’ll need to employ.”

Too close for comfort? A Somerville office in 2016. An expert says changes, including "de-densification," can be made in the workplace to make it safer for people when the economy reopens.Suzanne Kreiter

An expert on sick buildings says a number of doable steps can be taken to make returning to the office safer once the coronavirus crisis has waned.

Joseph Allen, a professor of exposure assessment science at the Harvard T.H. Chan School of Public Health, said Thursday that what is required is a “layered defense” strategy against the possibility that the virus is present in the air or on surfaces in a building.

Occupational safety and health experts have talked for decades about a “hierarchy of controls” for dealing with hazards in the workplace, Allen said. That framework can be applied to the coronavirus pandemic, though the hazard in question is an unseen virus, rather than a vat of chemicals in a factory.


The five components of the hierarchy, in order of effectiveness, are elimination, substitution, engineering controls, administrative controls, and personal protective equipment (PPE).

In the case of the coronavirus, elimination of the hazard could be accomplished by everyone continuing to work at home. “Personnel substitution” could be another option, he said: asking only the core people in the business to go into the office.

Under the category of engineering controls would be measures such as improvement of ventilation and filtration in the building, including the possible use of portable air purifiers.

Administrative controls would involve changes to reduce the density of people in a building, including changing work shifts, spreading people out, and limiting use of conference rooms, according to Allen. “You want to de-densify your building,” he said.

Finally, PPE such as masks could be used. People could be asked to wear cloth masks in common areas and elevators, for example, he said.

“There’s no silver bullet here,” he said. “We have to put in this full, layered approach across all of these controls."

He said there was a “bit of a common misperception” that making the changes would be costly.


“Broadly, these are strategies that people can put in and the costs are low or manageable,” he said.

Allen offered his framework as pressure builds to reopen the economy and experts and business leaders are thinking about the safest ways to to do it. The general consensus is that things won’t be the same.

A Kendall Square research institute, the Ragon Institute of MGH, MIT, and Harvard, plans to test the hypothesis that it can return to full operation without endangering its employees, by following a rigorous set of steps in a carefully controlled environment, the Globe reported. Some of the steps the institute is planning to take are akin to those suggested by Allen.

Allen said he was not arguing for a relaxation of restrictions currently in place, noting that he and many other scientists believe that the United States needs to continue practice social distancing, while at the same time ramping up health care capacity and increasing testing, which will enable contact tracing and isolation of infected people and quarantine of possibly infected people.

“I’m definitely on the side that we should be cautious here,” he said.

Instead, he said, he was “outlining what steps we should be taking to minimize risk in our buildings when we get back to work.”

“When the time is right," he said, "these are the strategies we’ll need to employ.”


Martin Finucane can be reached at