A pneumatic system includes a first line, a second line, and a valve. The first line is configured to be connected to a container, and to convey a flow of gas from a source to the container. The second line is arranged co-axially with the first line and is in communication with gas in the container. The valve is connected in series with the first line, between the source and the container. Furthermore, the valve is in communication with the second line and is configured to control the flow of gas through the first line as a function of a characteristic of the gas in the container, as communicated by the second line.