Some media have been claiming that carbon dioxide may slowly build up in the mask over time, causing medical issues related to the respiratory system such as hypercapnia (a condition arising from too much carbon dioxide in the blood). When wearing a face mask, a fraction of carbon dioxide previously exhaled is inhaled again with each respiratory cycle. An adult with healthy lungs produces approximately 5.6% by volume of CO 2. The human body utilizes oxygen and generates carbon dioxide, which is then exhaled in the expiration air. Especially, the use of face masks in public reduces the spread of the virus by minimizing the excretion of respiratory droplets from asymptomatic infected individuals or individuals who have not yet developed symptoms (Bourouiba, 2020). Physical distancing, good hand hygiene and the wearing of gloves and face masks are among the most frequent measures taken to prevent person-to-person transmission of the virus (SARS-CoV-2) responsible for the coronavirus disease (COVID-19) since the outbreak of the COVID-19 pandemic in early 2020 (Chu et al., 2020 Howard et al., 2020). Keywords: Face masks, Carbon dioxide, SARS-CoV-2, COVID-19 pandemic, COVID-19 However, concentrations in the detected range can cause undesirable symptoms, such as fatigue, headache, and loss of concentration. According to the literature, these concentrations have no toxicological effect. No differences were observed among the three types of face masks tested. 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. A small increase could be observed when walking at a speed of 3 km h –1 (leisurely walking pace). Doing office work and standing still on the treadmill each resulted in carbon dioxide concentrations of around 2200 ppm. The concentrations of carbon dioxide while not wearing a face mask varied from 500–900 ppm. Detected carbon dioxide concentrations ranged from 2150 ± 192 to 2875 ± 323 ppm. Measurements were made using a modified indoor air quality meter equipped with a nondispersive infrared (NDIR) CO 2 sensor. For the surgical mask, the concentration was determined under different conditions (office work, slow walking, and fast walking). In this study, the carbon dioxide concentration in the breathing zone was measured while wearing a surgical mask, a KN95 and a cloth mask. 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. 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). The measured concentrations have no toxicological effect when inhaled.Three types of face masks were tested under different conditions.Concentration of CO 2 in the breathing zone while wearing a face mask was determined.

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

The breathing zone