Testing buildings — not just people — could be an important way to stop the spread of the coronavirus.

Why it matters: People won't feel safe returning to schools, offices, bars and restaurants unless they can be assured they won't be infected by coronavirus particles lingering in the air — or being pumped through the buildings' air ducts. One day, even office furniture lined with plants could be used to clean air in cubicles.

The big picture: Prodded by more than 200 scientists, the World Health Organization now acknowledges there is emerging evidence of airborne transmission in crowded or poorly ventilated settings.

• In Florida, Texas and other Sun Belt states, a dramatic rise in COVID-19 cases has been linked to air-conditioned bars, house parties and other large gatherings.
• The virus thrives indoors in both heated and cooled environments if the humidity is below 40%, scientists say.

Driving the news:New research from the University of Oregon, in partnership with the University of California-Davis, suggests heating, ventilation and air conditioning systems could be contributing to the spread of the disease in health care facilities.

• There are some fairly easy fixes, like installing more sophisticated air filters, drawing more fresh air into buildings and cranking up the humidity, which tends to kill the virus.
• But when it's extremely hot or cold outside, some of these measures could overwhelm HVAC systems, ventilation experts say.

Environmental testing could provide early warnings of an outbreak, says Kevin Van Den Wymelenberg, director of the Institute for Health in the Built Environment at the University of Oregon.

A biotech startup called Enviral Tech teamed up with his lab to conduct weekly tests of 52 long-term care facilities in a half-dozen states in the Pacific Northwest. At least four showed signs of the virus.

• Springs Living, an assisted living center in Portland, detected the virus in an air duct three weeks into the pilot, after showing no signs in the previous tests.
• The management quickly tested all residents and staff, and found a handful of positive cases, though none of the individuals showed symptoms until five days later.
• They were quarantined while the building and HVAC system were thoroughly cleaned. No other cases developed and everyone survived.
• "We had a five-day head start" on the outbreak, said Springs Living CEO Fee Stubblefield, whose company is running similar tests at all 18 of its facilities.

How it works: Using Enviral Tech's test kits, building managers can collect up to four samples from various surfaces in a building, including duct work.

• The swabs are placed in a designated tube, and mailed overnight to its Eugene, Ore., lab for analysis, with results in 24 hours or less.
• The kits cost $300 each, or about $225 by weekly subscription, says Enviral Tech CEO Shula Jaron.
• "Testing your building is really the key to restarting the engine of the economy," says Van Den Wymelenberg.

What to watch: His lab is designing micro-environments that could provide office workers with their own supply of fresh air.

• HyPhy is a twist on the traditional office cubicle: it's a personal clean air pod that integrates a fern called Azolla into the furniture to provide personalized air circulation and purification.
• The plants, when treated with ultraviolet lights under the desk, may help kill pathogens while pumping localized fresh air into the breathing zone of the cubicle's occupant.