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.
The Mask. The mask is your window to the underwater world. It provides an air pocket so your eyes can focus and you can see clearly underwater. Your nose must be within the eye pocket so you can adjust for pressure changes (this is why swim goggles cannot be used for snorkeling).