Greg Smith had little time to spare when studies began suggesting the novel coronavirus can spread through shared air within buildings.

As a facilities management director for the King County Library System, Smith overseas the heating, ventilation and air conditioning (HVAC) systems in about four dozen buildings currently closed to non-staffers. He contacted the county’s HVAC maintenance contractor and they tested each of the systems — the oldest about 15 years — to ensure maximum air flow and filtration before library visitors are allowed back in.

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Given the cost of completely replacing HVAC systems can run $100,000 to $500,000 for smaller buildings and into the millions for bigger ones, specialists are instead finding creative ways of improving what’s already there.

Rod Kauffman, president of the local Building Owners and Managers Association (BOMA), a trade group with membership comprising about 70% of Seattle and Bellevue office buildings, said most members have increased their fresh air intakes. Others have upgraded filters and some have even installed the more expensive UV light disinfecting devices within systems.

Their scramble to make changes increased after more than 200 researchers recently pushed the World Health Organization to recognize that the coronavirus can spread through air currents. That followed a springtime University of Oregon study which found the virus present in a quarter of the vents in hospital rooms where COVID-19 patients were treated — suggesting it might spread through air separate from an infected person’s location.

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For Smith, that meant upgrading the standard filters within library HVAC systems to a version that traps smaller air particles and droplets.

He also began “flushing” the libraries of interior air more frequently throughout the day and replacing it with outside air that is cooled and then recirculated. Every evening, the buildings are additionally flushed for eight hours at a time.

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Rory Olson, vice president of service operations for MacDonald-Miller Facility Solutions, the HVAC specialists working with Smith, said the business has been “bombarded with calls’’ from building managers since April. That’s when the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) warned that HVAC mitigation might be needed to prevent people from becoming infected by airborne coronavirus droplets.

“Transmission of (coronavirus) through the air is sufficiently likely that airborne exposure to the virus should be controlled,” ASHRAE wrote. “Changes to building operations, including the operation of heating, ventilating, and air-conditioning systems, can reduce airborne exposures.”

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Solutions are tailored around a company’s specific HVAC system. In general, mitigation falls into four categories: ventilation, filtration, humidity and disinfection.