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.
Respiratory Protection: For conditions of use where exposure to the dust or mist is. apparent, a half-face dust/mist respirator may be worn. For emergencies or. instances where the exposure levels are not known, use a full-face positive-. pressure, air-supplied respirator. For exposure over the PEL/TLV and up to.