What is a key reason for purging air from gas systems?

Purging air from gas systems is essential primarily to decrease the risk of explosion during start-up. When air is present in a gas system, it creates a potentially explosive mixture when combined with gas. The presence of oxygen from the air increases the risk of combustion occurring unexpectedly, which can lead to explosions. By purging air, the system is filled with a gas that has a known composition and reduces the potential for an uncontrolled combustion event when the system is ignited. This practice not only enhances safety but also ensures that the gas can combust effectively and within the designed parameters of the system.

While the other options suggest important aspects related to gas systems, they do not directly address the critical safety issue of purging air specifically to mitigate explosion risk during the operation of gas systems.