This is a face mask used for protection against coronavirus, but it can be used in other situations. The main design is attributed to COVID-19 Makers or Coronavirus Makers, a group of people in Spain that is dedicated to helping healthcare workers and other personnel protect against the coronavirus, and help flatten the curve.

The manual is translated from https://www.thingiverse.com/thing:4233193 as asked by some non-spanish speakers.

Note: the mask version is not the same as the one in the manual, but a better one in my opinion. For the one in the manual go to the previous link.