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.
Individual Protective Equipment. MCU-2A/P Mask. The MCU-2A/P series mask (Air Force Technical Order 14P4-15-. 1) is designed to protect the face, eyes, and respiratory tract of. the user from tactical concentrations of chemical and biological. agents, toxins, and radioactive fallout particles.