Trends in Indoor Air

In this episode of the NAFA Podcast, recorded live at NAFA’s 2025 Technical Seminar, Dr. Joseph Allen, Director of the Healthy Buildings Program at Harvard T.H. Chan School of Public Health, delivers a compelling keynote on why healthy buildings are central to public health, productivity, and safety.

Dr. Allen explores how cleaner air improves cognitive function, why outdated ventilation standards fail to protect people, and how the COVID-19 pandemic reshaped the science and policy of indoor air. He shares actionable strategies for building owners, engineers, employers, and policymakers to improve indoor environments through better ventilation, filtration, and design standards.

Listeners will learn about the history of ventilation standards, the breakthrough shift in recognizing airborne transmission of COVID-19, the movement toward health-based ventilation targets, and the rise of low-cost indoor air monitoring tools that are transforming accountability in buildings worldwide.

Whether you work in air filtration, facilities management, public health, or are simply curious about the air you breathe, this episode offers practical takeaways and a vision for the future of healthy buildings.

00:00 – 00:31Introduction to the NAFA Podcast and its mission.

00:31 – 01:05Overview of the episode: Dr. Joseph Allen on the science and business case for cleaner indoor air.

01:05 – 01:28Practical steps for professionals, employers, and policymakers to improve indoor environments.

01:28 – 02:02Acknowledgments to NAFA and opening remarks.

02:02 – 03:02Audience quiz on indoor air and how much time people spend indoors (90%).

03:02 – 04:13Why buildings are missing from decades of public health studies and why this gap matters.

04:13 – 05:34Quiz continues: ventilation standards, particle exposure, and how much air comes from others in the room.

05:34 – 06:09Introduction to strategies for reducing respiratory disease indoors.

06:09 – 07:12Buildings as frontline tools during pandemics and early COVID-19 insights.

07:12 – 09:14Making the case for airborne transmission during the pandemic and why recognition was delayed.

09:14 – 10:24Modeling airborne transmission and demonstrating how ventilation and filtration reduce spread.

10:24 – 11:09Breaking into top medical journals and shifting decades of assumptions about transmission.

11:09 – 12:28The “first four healthy building strategies”: commissioning, ventilation, filtration, and portable air cleaners.

12:28 – 13:24Portable air cleaners: effectiveness, placement, and the importance of mixing.

13:24 – 14:38Why airflow and mixing are critical to reducing infection risks.

14:38 – 15:29The challenge of setting health-based ventilation targets—moving beyond “acceptable” standards.

15:29 – 16:51Historical perspective: ventilation targets in the 1800s and how they regressed in the 1970s.

16:51 – 18:10COVID-19 guidance: 4–6 air changes per hour and the need for clear targets.

18:10 – 19:56Consensus building: Lancet Commission and the push toward 30 CFM/person or 5 ACH.

19:56 – 21:14Adoption of new standards by ASHRAE, CDC, and state health departments.

21:14 – 22:22A major turning point: reframing ventilation as a cornerstone of public health.

22:23 – 23:14NAFA certifications and professionalism in air filtration.

23:14 – 24:18Public awareness shift: indoor air quality on the front page of The New York Times and 60 Minutes.

24:18 – 26:01Technology shift: rise of low-cost air quality monitors and their impact on accountability.

26:01 – 27:34The public’s new ability to “interview” buildings and the power shift in knowledge.

(Episode continues with additional research insights and closing commentary.)

Episode Timestamps