Indoor Air Quality: Can It Strengthen Pandemic

Why does indoor air matter for pandemic preparedness?

The WHO appeal for an international pandemic agreement highlighted the need to prepare before another major outbreak. That appeal was published on March 20, 2024; the World Health Assembly subsequently adopted the WHO Pandemic Agreement on May 20, 2025. These are established milestones, rather than announcements made today. A practical question within the broader preparedness agenda is how everyday buildings can reduce opportunities for respiratory transmission. Sources: [WHO's original appeal](https://www.who.int/news/item/20-03-2024-call-for-urgent-agreement-on-international-deal-to-prepare-for-and-prevent-future-pandemics) and [agreement adoption announcement](https://www.who.int/news/item/20-05-2025-world-health-assembly-adopts-historic-pandemic-agreement-to-make-the-world-more-equitable-and-safer-from-future-pandemics).

For infections transmitted through the air, ventilation brings in outdoor air to dilute infectious particles, while filtration removes particles from air passing through a filter. Crowding, prolonged exposure and inadequate ventilation can allow respiratory particles to accumulate indoors. WHO's ventilation roadmap addresses healthcare, residential and other buildings, making air management relevant across settings. Its application to future respiratory threats is a preparedness rationale; it does not establish that ventilation can prevent every type of pandemic. [WHO ventilation roadmap](https://www.who.int/publications/i/item/9789240021280).

How much ventilation helps reduce airborne virus exposure?

Air changes per hour describe airflow relative to a room's volume. CDC's workplace guidance suggests aiming for five or more clean-air changes per hour through outdoor-air ventilation, filtration or other appropriate air-cleaning methods. Filtration contributes equivalent air changes because it removes particles from recirculated air. This target is a practical guide, and higher occupancy or greater vulnerability among occupants may justify additional protection. [CDC airflow guidance](https://www.cdc.gov/niosh/ventilation/prevention/aim-for-5.html).

The number should not be interpreted as a guarantee that every part of a room becomes safe after a fixed interval. Air mixes unevenly, and an infectious person can continue releasing particles while the system operates. CDC also acknowledges uncertainty about the optimal ventilation strategy and the size of its effect on actual infections. Reducing airborne particle concentrations supports prevention, but it does not establish a universal percentage reduction in illness. [CDC evidence and limitations](https://www.cdc.gov/niosh/ventilation/prevention/aim-for-5.html).

How can buildings improve ventilation and filtration?

Building managers should first assess how ventilation operates during normal occupancy. CDC recommends MERV 13 filters, or the highest efficiency a heating, ventilation and air-conditioning system can accommodate without impairing performance. Compatibility matters: a filter that creates excessive resistance can reduce airflow. Portable HEPA units can supplement existing systems, particularly where upgrades are difficult, but their placement and airflow must suit the space. [CDC ventilation and filtration guidance](https://www.cdc.gov/niosh/ventilation/faq/index.html).

EPA describes HEPA filtration as capable of capturing at least 99.97% of particles measuring 0.3 micrometers under specified conditions. That figure describes filter performance, not the percentage of infections prevented in a room. The amount of air actually processed also matters: an efficient filter in an undersized or rarely operated device may provide limited room-level protection. [EPA explanation of HEPA filters](https://www.epa.gov/indoor-air-quality-iaq/what-hepa-filter).

When choosing a portable unit, EPA advises matching its clean air delivery rate, or CADR, to the room. Higher ceilings and larger spaces require additional capacity. Noise matters because people must be willing to run the device at an effective setting, and filters need replacement according to manufacturer instructions. Avoid devices that intentionally generate ozone, which can irritate the lungs. These operating details determine whether a purchase delivers sustained improvements in indoor air. [EPA guide to home air cleaners](https://www.epa.gov/indoor-air-quality-iaq/guide-air-cleaners-home).