How clean is the air in your school or workplace? Hint: Many places are lacking.

A teacher wearing a mask looked out a classroom window in Boston in 2020.David L. Ryan/Globe Staff

Two years into an airborne pandemic, many buildings around the country are still poorly ventilated and lack sufficient filtration systems to prevent the spread of COVID-19 and other infections, experts say.

The White House on Tuesday renewed its push to improve indoor air quality at workplaces and schools at a time when mask mandates have been largely discontinued and another more transmissible version of the virus, known as BA.2, is widely circulating.

“For decades, Americans have demanded that clean water flow from our taps and pollution limits be placed on our smokestacks and tailpipes,” Dr. Alondra Nelson, head of the White House Office of Science and Technology Policy, said during a White House virtual event. “Our indoor air should be clean and healthy too. It’s just as important as the food we eat and the water we drink.”

In Massachusetts, with its abundance of historic buildings and aging schools with decrepit heating and cooling systems, the quality of indoor air is also a concern. At least half of the ventilation systems in public schools have yet to be upgraded, one expert estimated.

Tiny airborne particles of the coronavirus that causes COVID can remain in circulation for minutes or hours after an infected person has been in a room. Moreover, many schools, offices, hotels, and other places designed to be energy efficient do not have windows that open, fueling the initiative for improved ventilation.

The Biden administration earlier this month launched a Clean Air in Buildings Challenge aimed at property owners and operators. It includes guidance on how to bring more fresh air into ventilation systems and enhance filtration units. But the administration has yet to release regulations or dedicate new funds to the initiative.

Some of the researchers who spoke during the White House event said top health leaders in the United States and at the World Health Organization were slow to acknowledge for months into the pandemic that the virus was airborne, and that worsened outcomes.

“There was this sort of institutional inertia to admitting that . . . we got something wrong and we didn’t recognize emerging evidence when it was coming out,” said Zeynep Tufekci, an associate professor at the University of North Carolina at Chapel Hill, who studies social impacts of technology.

Experts on indoor air quality say upgrading systems in buildings to reduce the risk of COVID transmission will pay dividends for years. The improvements could also reduce the risk of spreading the flu and other airborne illnesses, as well as improve working conditions for students and employees, with studies showing that better quality air boosts concentration and performance.

”When businesses do this, they can see a 10 percent benefit to the bottom line of an organization,” said Joseph Allen, associate professor at Harvard T.H. Chan School of Public Health.

Researchers outlined three basic steps toward improving indoor air quality: bringing more clean indoor air into a building’s heating and cooling system; using high-quality air filters known as HEPA or MERV-13, especially if adequate ventilation is not possible; and disinfecting the air by using ultraviolet lights inside air conditioning systems or mounted near ceiling fans that draw the air up so the lights can disarm germs.

Increasing ventilation and filtration essentially dilutes the amount of coronavirus in a room and decreases the risks for inhaling large doses of the virus. Researchers say HVAC systems that bring in fresh air five to six times per hour are a good target, or adding filtration that produces the equivalent of an increased amount of fresh air. But many buildings are still not achieving those goals.

“We’ve designed our buildings to bare minimum standards, not health-based standards,” Allen said. “We use bare minimum filters that are designed to protect the equipment, not designed to protect the people.”

But there usually is no simple way for people to know the quality of the air in their office or school. Researchers have often used carbon dioxide detectors as a proxy for how well a room is ventilated; the higher levels of CO2, which people exhale, the less fresh air is coming into a building.

Allen suggested people ask about carbon dioxide detectors in their buildings and also for details about the specific upgrades building owners or operators have made to their ventilation and filtration systems.

One area that has sparked concern during the pandemic is the quality of air aboard airplanes. The Biden administration recently extended its mask mandate for planes and public transportation to mid-April, triggering protests from airline executives.

Some studies have suggested that COVID-19 can be transmitted aboard planes, and have concluded that masks, limiting conversation, and some proactive seating strategies, such as leaving middle seats open and skipping some rows, may reduce transmission.

Another concern is the nation’s nearly 100,000 public school buildings.

In June 2020, the US Government Accountability Office released a report that found about half of the nation’s public schools needed to update or replace multiple systems such as heating, ventilation, and air conditioning or plumbing. It estimated that one-third of the schools needed to update their air-handling systems, known as HVACs.

When the Globe on Tuesday asked whether things have improved since then, a White House spokesperson referred the question to the Center for Green Schools, a D.C.-nonprofit that researches the issue. Anisa Heming, the center’s director, said there is no national data about the condition of school facilities, nor regular comprehensive tracking of the issue. The center late last year surveyed 89 school districts with over 2.6 million students.

It found the vast majority chose to upgrade ventilation, but most also encountered challenges because their building HVAC systems are not designed to support the larger recommended intake of fresh outdoor air. Many also said their systems were not powerful enough to accommodate the recommended higher grade filters.

“Focus group participants indicated that school districts are having a hard time moving away from measures that were considered effective at the start of the pandemic but are no longer proven to be as effective at preventing COVID-19, such as increased surface disinfection,” Heming said in an e-mail.

“Daily, stringent cleaning regimens are costly and are not the most effective way to prevent the spread of COVID-19, but they are visible and still have strong support among parents and community members.”

In Massachusetts, at least half of public schools have decades-old ventilation systems that haven’t been upgraded to filter out airborne viruses, said Ken Wertz, executive director of the Massachusetts Facilities Administrators Association, which represents facilities directors in public schools and municipal buildings.

“It’s still a mixed bag out there,” Wertz said.

“Everyone has seemed to buy portable [air cleaning] units as part of the quick COVID solution But that’s a stopgap,” he said. “Those appliances are not designed to run 24/7, and in the next five years they will burn out.”