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Special Issue on COVID-19 Aerosol Drivers, Impacts and Mitigation (X)

ORIGINAL RESEARCH
https://doi.org/10.4209/aaqr.2020.07.0403

at concentrations above 1000 ppm and include drowsiness and loss of attention (Guais et al.,
2011). A portion of the human population has been described as being sensitive to fluctuating
CO2 concentrations. As a vasodilator, the effect on people prone to headache has also been
discussed. For example, Lim et al. (2006) administered a survey to healthcare workers to
determine risk factors associated with the development of headaches. Approximately 40% of the
respondents reported wearing face masks was associated with headaches. This study did not,
however, report the inhaled CO2 concentrations. Satish et al. (2012) suggested in their study that
even moderately elevated CO2 concentrations (approximately 2500 ppm) have the potential to
affect decision-making.

4 CONCLUSIONS
The concentrations of carbon dioxide measured in the breathing zone while wearing a face
mask ranged between 2150 and 2875 ppm depending on the type of activity. The concentrations
of carbon dioxide without wearing a face mask varied from 500–900 ppm, corresponding to
normal carbon dioxide concentrations in indoor environments. Doing office work and standing
still on the treadmill each resulted in carbon dioxide concentrations of around 2200 ppm. A small
increase of approximately 300 ppm 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 tested face masks. According to
the literature, these concentrations have no toxicological effect when inhaled. However,
concentrations between 1,000 ppm and 10,000 ppm can cause undesirable symptoms such as
fatigue, headache and loss of concentration. This may be relevant for those segments of the
population required to wear face masks over prolonged periods of time such as students, bus
drivers or cashiers as well as persons with respiratory diseases. Wearing face masks only when
strictly necessary may reduce these undesired side effects.

ACKNOWLEDGMENTS
We thank Ivana Bianchi and Josefa Barrero-Moreno for comments that greatly improved the
manuscript.

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Volume 21 | Issue 2 | 200403

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