Using the Harris 25GX-145-540 Single-Stage Pressure Regulator is simple. First, make sure the inlet connection is properly attached to the oxygen source using the CGA 540 connection. Then, adjust the pressure using the ABS black plastic knob. The gauges will show you the supply and delivery pressures. For safety, always follow the CGA E - 4 and UL® guidelines. When not in use, store it in a dry place. To maintain it, clean the exterior regularly. Check the diaphragm and seat for any signs of wear. Consider using the recommended steel gauge guards (red for fuel and green for oxygen) to protect the gauges. If you notice any problems with pressure regulation or other issues, stop using it and get it checked by a professional.