As to the question of rules regarding when and where peaceful protests may be held, that's highly dependent on the specific location of the protest.
The venturi mask, also known as an air-entrainment mask (and sometimes by the brand name VentimaskÂ®), is a medical device to deliver a known oxygen concentration to patients on controlled oxygen therapy.
These masks are used by people who breathe through their mouth during sleep and do not wish to use, or have not had success with, a nasal mask and chinstrap. In general, full face CPAP masks are heavier and bulkier than nasal CPAP masks simply because they cover both the nose and mouth.