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.
Half Facepiece & Full Facepiece Gas Mask/Chemical Cartridge Respirators. These chemical and gas masks are also known as air-purifying respirators because they filter or clean chemical gases and particles out of the air as you breathe.