Final Answer:
You should never use oxygen or compressed air to leak-check hardware because both substances pose a significant risk of combustion or explosion when they come into contact with flammable materials.
Step-by-step explanation:
The fundamental reason for avoiding the use of oxygen or compressed air in leak-checking hardware lies in the potential for combustion or explosion. When oxygen is present in the presence of flammable substances, it significantly increases the risk of fire.
Oxygen supports combustion, and even a small ignition source in the vicinity can lead to a rapid and intense fire. Similarly, compressed air, which often contains a high concentration of oxygen, can create a hazardous environment when combined with flammable materials.
In practical terms, the dangers associated with using oxygen or compressed air for leak-checking are rooted in the principles of the fire triangle. The fire triangle consists of three elements: a fuel source, an oxidizing agent (such as oxygen), and an ignition source.
When all three elements are present, the conditions for combustion are met. In the context of leak-checking hardware, introducing oxygen or compressed air increases the oxidizing agent's concentration, raising the risk of fire or explosion if a flammable substance is present. Therefore, alternative, inert gases such as nitrogen are commonly used for leak-checking applications to minimize these risks and ensure a safe testing environment.