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.
A procedure mask is used for performing patient procedures, or when patients are in isolation to protect them from potential contaminants. They are used for 'respiratory etiquette' to prevent people from spreading germs via talking, coughing, or sneezing.