evidence: There have been concerns that face masks can reduce oxygen intake, and can lead to low blood oxygen levels, known as hypoxemia. However, masks are made from breathable materials that will not block the oxygen your child needs. Masks have not been shown to affect a child's ability to focus or learn in school. The vast majority of children age 2 or older can safely wear face masks for extended periods of time, such as during preschool or at child care. This includes most children with special health care needs. [...] No, wearing a face mask will not affect your child 's lungs from developing normally. This is because oxygen flows through and around the mask, while blocking the spray of spit and respiratory droplets that may contain the virus. Keeping your child's lungs healthy is important, which includes preventing infections like COVID-19. [...] No. There have been false reports that face masks can lead to carbon dioxide poisoning (known as hypercapnia) from re-breathing the air we normally breathe out. But this is not true. Carbon dioxide molecules are very tiny, even smaller than respiratory droplets. They cannot be trapped by breathable materials like disposable masks. In fact, surgeons wear tight fitting masks all day as part of their jobs, without any harm.