New research by the University of Oregon and the University of California-Davis points to HVAC systems as spreaders of the coronavirus, though the study is still preliminary.

The research comes when the possibility that the coronavirus spreads via tiny particles (aerosols) in the air, rather than larger droplets alone, has been acknowledged by the World Health Organization, or to use its terms, such transmission "cannot be ruled out."

If transmission via particles through HVAC systems is confirmed, that might impact guidelines for indoor spaces, the BBC reports, and spur testing of buildings as well as people in the effort to detect the virus and prevent transmission, according to Axios.

"The presence of SARS-CoV-2 RNA was detected in approximately 25% of samples taken from nine different locations in multiple air handlers," the University of Oregon paper notes. SARS-CoV-2 is the formal name for the coronavirus that causes COVID-19.

"While samples were not evaluated for viral infectivity, the presence of viral RNA in air handlers raises the possibility that viral particles can enter and travel within the air handling system of a hospital, from room return air through high efficiency MERV-15 filters and into supply air ducts," the paper said.

The spread of the coronavirus via HVAC is of particular concern during the hottest and coldest months of the year. A Harvard infectious disease specialist has suggested that increased air conditioning use in the South since the beginning of hot weather might be a factor in spiking COVID-19 cases in that region, as the heat keeps people indoors more.

“As people go indoors in hot weather and the rebreathed air fraction goes up, the risk of infection is quite dramatic,” Edward Nardell, professor of medicine and of global health and social medicine at Harvard Medical School, told the Harvard Gazette.

As the understanding of the role of HVAC in the pandemic grows, along with the idea that it has a role in spreading the disease, commercial building managers are questioning the idea that buildings need to be mostly cut off from outside air, The Wall Street Journal reports.

HVAC manufacturers are responding as well, offering equipment that filters indoor air more completely, and brings more outdoor air into the system. UV light is also being used to control the spread of the virus.

“More fresh air and cleaner air are the direction that customers are going," Johnson Controls President of Global Products Jeff Williams told the WSJ.

Building testing tech is also being rolled out. For example, Oregon-based EnviralTech, a pandemic-era startup originally focused on testing surfaces for coronavirus, has lately expanded into air testing for the virus. The company places an air intake device fitted with a filter that captures SARS-CoV-2 in a closed space or HVAC system and then tests the filter for the presence of the virus, TV station KVAL reports.