How much ventilation is needed to limit COVID-19 aerosol-based transmission?

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.

We don’t know. There is no universal answer applicable for all scenarios.

The quantity of ventilation needed depends on the amount and nature of the SARS-CoV-2 aerosols. If the emission characteristics of SARS-CoV-2 and the dose-response curve would be known, then it would be possible to calculate the rate of ventilation needed to prevent occupants’ exposures exceeding a predefined safe dose. At the moment of writing there is however insufficient scientific knowledge to define this rate. Based on what we know about the variables involved, the required airflow rates can vary substantially depending on the situation.

In many buildings, the real ventilation rates are lower than the requirements specified in building regulations. As explained in the AIVC FAQ (1), minimum ventilation rate requirements worldwide for dwellings, office and schools are available in the technical note 55 "A review of international ventilation, airtightness, thermal insulation and indoor air quality criteria" (2), but also in later publications such as (Brelih and Seppännen, 2011) (3) and (Laverge et al., 2013) (4). From a virus transmission prevention perspective, airflows or air change rates at the room scale (available in these references), is more relevant to use than ventilation rate at the whole building scale.

Before drastically altering the airflow pattern in a building to reduce the exposure to SARS-CoV-2 aerosols, it is important to analyze the location of the zones with potentially higher sources of SARS-CoV-2 emissions (high occupancy, high emitting occupants/activities, quarantine rooms, etc.), and also the zones to protect (vulnerable occupants for instance), in order to enclose or extract at the point of source to avoid contamination of occupied spaces.

Authors

Gaëlle Guyot, Cerema, Univ. Savoie Mont Blanc, Jelle Laverge, UGent & Willem de Gids, VentGuide

References

1. AIVC, Frequently Asked Questions. How much ventilation is needed?
2. M.J. Limb, A review of international ventilation, airtightness, thermal insulation and indoor air quality criteria, 2001. AIVC Technical note 55. 203p.
3. N. Brelih, O. Seppänen, Ventilation rates and IAQ in european standards and national regulations, in: In : Proceedings AIVC Conference, Brussels, Belgium, 2011.
4. J. Laverge, X. Pattyn, A. Janssens, Performance assessment of residential mechanical exhaust ventilation systems dimensioned in accordance with Belgian, British, Dutch, French and ASHRAE standards, Building and Environment. 59 (2013) 177–186. https://doi.org/10.1016/j.buildenv.2012.08.018.
5. AIVC. AIVC Newsletter Special Issue on COVID-19. February 2021.