... disaster relief. It adopts positive pressure principle to supply oxygen, which makes the pressure in the facemask exceed the atmospheric ... design, crush-proof, good impermeability, safe and stableHYZ4 cooling canister chamber equips with drainage, which protects against the breathing ... protective time/Duration: ≥240 minutes(i.e.4h)Rated pressure of the cylinder: 20MPaRated reserves in the cylinder: 540 ...