Is ventilation the same as air movement in relation to COVID-19?

REMARK: This Q&A was part of the AIVC special COVID-19 newsletter published in February 2021. To subscribe to the newsletter please click here.

No. Ventilation is air exchange between inside and outside. It dilutes the concentration of contaminants, and hence helps to control aerosol-based cross-infection risk of COVID-19.

There are several ways to ventilate a room:

Figure 1: Examples of the four basic principles of ventilation: full displacement, full mixing local displacement and local exhaust (AIVC TN 68: Residential Ventilation and Health, 2016)

Full displacement ventilation is normally only applied for specific applications such as clean rooms and operating theaters.

In most buildings, ventilation systems try to achieve complete or full mixing.

Air movement always exists in a room. It can be driven by thermal and mechanical forces. Ventilation causes air movement and hence transport of air within one room, but can also cause air transport from one room to another. Air movement in a room contributes to the spread of aerosols and to the long-range airborne transmission of COVID-19.  With effective mixing ventilation, the aerosol concentration is almost constant from 1-1.5 m distance from an infection source. In practice, there may however be differences in exposure over longer distances, depending on the ventilation supply air velocity, or on local air flow patterns in a room.

Author

Willem de Gids, VentGuide

References

1. AIVC TN68 – Residential Ventilation and Health, 2016
2. AIVC. AIVC Newsletter Special Issue on COVID-19. February 2021.