The directions on the original mask are as follows:
SUPPLEMENTAL OXYGEN (O2) MASK
1. Connect O2 tube to O2 supply or remove 22MM / O2 fitting and connect to bag.
2. Seal mask over patient's mouth and nose.
3. Set appropriate O2 flow rate for patient.
NB: MASK VENTS ALLOW FOR:
1. Patient exhalation
2. Escape of excess O2 if flow rate is too high.
3. Patient inhalation of supplemental ambient if O2 flow rate is too low.