Businesses around the U.S. are committing to becoming emissions-free as part of an effort to reduce their global footprint, but these changes are facing challenges as the coronavirus pandemic has not been contained.

In particular, building owners are tasked with reducing the spread of the coronavirus through outdoor air filtration, but the added cost and energy use is working against their goal to reduce their real estate emissions.

This presents an issue for building owners that are looking to keep their tenants safe from the coronavirus while making their properties more energy efficient. As much as 39% of all energy-related carbon emissions come from buildings and construction, a 2019 report by the United Nations Environment Programme said.

The issue is further complicated as some states and cities have aggressive emissions goals for property owners, which face hefty fines if they don’t comply. New York passed a bill in 2019 that set emissions limits for buildings to help reduce carbon emission by 40% by 2030 from its 2005 levels. If a property owner fails to comply, fines as high as millions of dollars could be enforced in 2024, the Wall Street Journal reported.

Studies have also indicated that the coronavirus is airborne and can live in indoor areas, which has prompted ASHRAE, formally known as the American Society of Heating, Refrigerating and Air-Conditioning Engineers, to say in April that HVAC systems should be run for 24 hours a day to help bring more outdoor air inside.

HVAC costs in office buildings have increased by 36% during the pandemic because of the practice, real estate tech firm, Enertiv said. The pandemic was also used by some landlords to upgrade their building’s systems, which could help offset the costs to run their HVAC system all-day-long or when people are present, the news outlet said.

“Somewhere between nothing and 100% outside air 100% of the time is a line at which what the landlord is doing is very, very reasonable,” Brenden Millstein, chief executive at Carbon Lighthouse, a company that works with building owners to reduce emissions, told the Journal.