What must be attached to each of the control valves before using a gas container?

Attaching a regulator to each of the control valves before using a gas container is essential for the safe and effective use of compressed gases. A regulator plays a crucial role in controlling the pressure of the gas as it is released from the container. It ensures that the gas is delivered at a safe and usable pressure level for the intended application, preventing potential hazards such as over-pressurization and equipment damage.

Additionally, the regulator allows for precise adjustments to the gas flow rate, making it easier to handle various tasks that require specific gas flow requirements. This safety measure is vital for both the user and the equipment involved in the operation.

While other options like a pressure monitor, control handle, and emergency shutoff may contribute to the overall safety and functionality of the gas handling process, the regulator is specifically essential in managing the pressure of gases released from containers. Therefore, it is a fundamental piece of equipment that must be utilized before any operational use of non-flammable compressed gases can take place.