Good ventilation and airflow can help reduce the spread of viruses in shared indoor spaces. But during big wildfires, like the ones in California that are sending smoke across the United States right now, or in areas with high levels of everyday air pollution, bringing in air from the outside isn’t a good option. Experts say the unhealthy air from fires in California can actually make people more susceptible to COVID-19 because their lungs and immune systems get overtaxed. So better filtration gets a lot more important. Molly speaks with Jeffrey Siegel, a professor of engineering at the University of Toronto who specializes in indoor air quality. He says whether it’s a standalone device or smart building technology, there are options.