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Otmar Geiss*
European Commission, Joint Research Centre (JRC), Ispra, Italy


Effect of Wearing Face Masks on the Carbon Dioxide Concentration in the Breathing Zone

Special Issue on COVID-19 Aerosol Drivers, Impacts and Mitigation (X) 2021 – Volume 21Volume 21, Issue 2, February 2021  07 October 2020  Reach: 50534 EmptyCOVID-19

Effect of Wearing Face Masks on the Carbon Dioxide Concentration in the Breathing Zone

Otmar Geiss  

European Commission, Joint Research Centre (JRC), Ispra, Italy

Received: July 15, 2020
Revised: October 1, 2020
Accepted: October 6, 2020

Copyright The Author’s institutions. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are cited. 
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Cite this article:

Geiss, O. (2021). Effect of Wearing Face Masks on the Carbon Dioxide Concentration in the Breathing Zone. Aerosol Air Qual. Res. 21, 200403.


  • Concentration of CO2 in the breathing zone while wearing a face mask was determined.
  • Three types of face masks were tested under different conditions.
  • The measured concentrations have no toxicological effect when inhaled.


The use of face masks is among the measures taken to prevent person-to-person transmission of the virus (SARS-CoV-2) responsible for the coronavirus disease (COVID-19). Lately, concern was expressed about the possibility that carbon dioxide could build up in the mask over time, causing medical issues related to the respiratory system. In this study, the carbon dioxide concentration in the breathing zone was measured while wearing a surgical mask, a KN95 and a cloth mask. For the surgical mask, the concentration was determined under different conditions (office work, slow walking, and fast walking). Measurements were made using a modified indoor air quality meter equipped with a nondispersive infrared (NDIR) CO2 sensor. Detected carbon dioxide concentrations ranged from 2150 ± 192 to 2875 ± 323 ppm. The concentrations of carbon dioxide while not wearing a face mask varied from 500–900 ppm. Doing office work and standing still on the treadmill each resulted in carbon dioxide concentrations of around 2200 ppm. A small increase could be observed when walking at a speed of 3 km h–1 (leisurely walking pace). Walking at a speed of 5 km h–1, which corresponds to medium activity with breathing through the mouth, resulted in an average carbon dioxide concentration of 2875 ppm. No differences were observed among the three types of face masks tested. According to the literature, these concentrations have no toxicological effect. However, concentrations in the detected range can cause undesirable symptoms, such as fatigue, headache, and loss of concentration.

Keywords: Face masks, Carbon dioxide, SARS-CoV-2, COVID-19 pandemic, COVID-19

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