Joseph Allen, DSc, assistant professor of exposure assessment science and director, Healthy Buildings Program, Harvard University.

Shelly Miller, PhD, environmental engineer, University of Colorado-Boulder.

Linsey Marr, PhD, professor of civil and environmental engineering, Virginia Tech.

Shelly Miller blog: “A Hopefully Helpful Short Report on Air Cleaners.”

Clinical Infectious Diseases: “It Is Time to Address Airborne Transmission of Coronavirus Disease 2019 (COVID-19).”

Indoor Air: “Ventilation and health in non‐industrial indoor environments: report from a European Multidisciplinary Scientific Consensus Meeting (EUROVEN).”

Environmental Protection Agency: “Air Cleaners and Air Filters in the Home,” “Indoor Air Quality: What is a HEPA filter?” Guide to Air Cleaners in the Home,” “Air Cleaners, HVAC Filters, and Coronavirus (COVID-19).”

Association of Home Appliance Manufacturers: “Facts About Clean Air.”

California Air Resources Board: “California Certified Air Cleaning Devices.”

Consumer Reports: “Best and Worst Air Purifiers of 2020,” “What You Need to Know About Air Purifiers and the Coronavirus.”

CNET: “Best air purifiers for 2020: Dyson, Coway, Molekule and more,” “Do air purifiers protect against COVID-19? What about wildfire smoke?”

Harvard-CU Boulder Portable Air Cleaner Calculator for Schools.

Mayo Clinic: “Can a home air purifier system protect you against COVID-19?”

NPR: “Coronavirus FAQ: How Do I Protect Myself If The Coronavirus Can Linger In The Air?” “Coronavirus FAQ: Is It A Good Idea To Buy An Air Cleaner For My Home?”

The Conversation: “How to use ventilation and air filtration to prevent the spread of coronavirus indoors.”

Vox: “Coronavirus is in the air. Here’s how to get it out.”

MD Anderson Cancer Center: “Can air purifiers protect you from COVID-19?”

National Library of Medicine (PubMed): “What is an effective portable air cleaning device? A review.”

WebMD: “Colleges and Universities: The New COVID Hot Spots,” “Coronavirus and Apartments: What’s the Risk?” “CDC Says Once Again Breathing Can Spread COVID.”

CNN: “Fauci: ‘There’s good enough data to say that aerosol transmission does occur.’ ”

NBC News: “Fauci calls Amy Coney Barrett ceremony in Rose Garden ‘superspreader event.’ ”