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.
There are several models of non-rebreather masks available in the market with similar designs. The mask fits over the mouth and nose and elastic straps wrap around the ears or the head. A one-way valve in the mask prevents exhaled air from entering into the tubing or bag containing the oxygen that is to be inhaled.