What should the cylinder service valve be prior to making a hose connection to the cylinder?

The correct practice before making a hose connection to the cylinder is to ensure that the cylinder service valve is closed. This is crucial for safety reasons, as opening the valve before making the connection can lead to gas escaping uncontrollably, increasing the risk of fire or explosion. By having the valve closed, you can safely attach the hose without the risk of gas leaking until you are fully prepared to open the valve afterward, which allows for safe inspection and connection procedures.

It is also important to remember that connecting hoses to a valve that is partially opened can create a hazardous situation, as it might lead to an inadvertent release of gas, and leaving the valve opened while connecting could result in immediate exposure to gas, which is dangerous. Therefore, ensuring the valve is closed is the standard safety protocol in such situations.