evidence: No. Children can safely wear masks all day. There’s a myth that wearing masks for long hours could mean breathing in too much carbon dioxide (CO2), which could lead to hypercapnia -- CO2 poisoning. But that’s not true. Evidence shows that CO2 molecules are small enough to pass through the pores in your mask, so it’s not possible for children to get CO2 poisoning by wearing masks at school. [...] Not at all. Wearing masks won’t compromise your child’s immunity or increase their risk of catching COVID or other infections. In fact, because face masks cover your nose and mouth, they stop your child from constantly touching their face. [...] Fact: Carbon dioxide can linger behind an N95 mask if you wear it for several hours, causing mild problems such as a headache, dizziness, or fatigue. But this risk is low with cloth and surgical masks.