During this pandemic, the simple act of walking into a building can feel like entering a biohazard area. With a virus that’s primarily transmitted through the air, being inside almost any space is a risk. But not all spaces are equally risky. A new certification system lets building owners quickly convey the safety of their indoor spaces to occupants.

Global safety science company UL has created a Verified Healthy Buildings certification, offering building owners and operators the chance to prove to people that they’ve done as much as they can to reduce the potential risk of contracting the virus indoors. About 400 buildings and spaces have received the mark so far, and a total of 175 million square feet of buildings have either been verified or are in the process of being verified. That includes properties owned and operated by some of the biggest commercial real estate holders, including Brookfield Properties and Brandywine Realty Trust, as well as entertainment venues like the Walt Disney Concert Hall in Los Angeles.

The certification focuses primarily on air, according to Sean McCrady, director of assets and sustainability for real estate and properties at UL. “In many respects air quality is the bedrock of optimizing the indoor environment overall,” he says. “Because that’s how people get sick; it’s a lack of ventilation in crowded spaces. We didn’t need to reinvent the wheel, we just need to have that much more focus on what’s always been important.”