When you connect a fresh cylinder, the most important check is to confirm that air is actually flowing and that the gauges reflect normal pressure before you proceed. Opening the cylinder valve slowly allows the regulator to prime and lets you observe whether air is being delivered to the facepiece. You should see the high‑pressure cylinder gauge rise to the expected operating range and you should detect airflow at the facepiece. If there’s no flow or the gauges show an abnormal or no pressure, there could be a leak, a mis-seated cylinder, or a regulator problem, and you should stop and address that before continuing. The color of the valve handle, the operator’s watch time, or the alignment of any passer do not verify that the air supply is ready and safe, so they aren’t sufficient checks for resuming work.