The alt text: A figure showing a spirometry mask either alone, or with a small piece of N95 material less than 10% the size of the full respirator taped over the hole, as used in a 2015 clinical trial widely cited during the pandemic as evidence of "harms" from N95s. To breathe the same volume of air at the same rate through 1/10th the cross sectional area, it has to move 10 times faster. This means flow resistance is increased by a factor of 10 - this is pretty intuitive (unless you're a clinical triallist, apparently), it's the same thing that makes it harder to breathe through a drinking straw than just your open mouth. This means the entire trial was performed under conditions equivalent to wearing 10 N95s on top of one another at once, and everyone involved and everyone who cited this study as meaningful should go and do something they are better equipped to handle than science, like watching paint dry. But since it is a clinical trial, EBM mindlessly treats it as the highest form of evidence - and since almost nothing gets retracted in clinical journals no matter how crappy it is, EBM processes keep using it. The image is from here: https://aricjournal.biomedcentral.com/articles/10.1186/s13756-015-0086-z/figures/2
Be sure to remember this whenever you hear the words "Masks don't work! They're bad for you!"
