Claim: Wearing a mask can cause hypercapnia, by making you breathe in too much carbon dioxide.
Fact-check: Ordinary face masks are not harmful - Full Fact
Verdict: this is not true. wearing a mask is safe for most people. there may be rare instances of harm involving  tight-fitting n95 or ffp2 masks.
Organisation: Full Fact
Author: Leo Benedictus
Date published: 2020-08-04T00:00:00