At the heart of the 3M™ Scott™ Sigma 2 set is a simple and reliable two-stage pneumatic system. A first breath activated positive pressure demand valve provides low breathing resistance and excellent dynamic performance - particularly at high flow rates. A first stage pressure reducing valve features only two moving parts and accepts cylinder pressures of up to 300 bar without adjustment. A cylinder connector assembly with standard breathing air thread is fitted, with an easily removed bronze filter to protect the pneumatics.