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.
Medical masks (surgical/procedure masks) are loose fitting masks that cover the mouth and nose. A respirator is designed to reduce exposure to airborne contaminants. Known airborne pathogens include TB, SARS, Anthrax, and Hanta virus.