Which of the following mediums is prohibited in testing a fuel gas piping system?

• A. Nitrogen
• B. Carbon Dioxide
• C. Oxygen
• D. Air

Answer: (C)

Using oxygen to test a fuel gas piping system is prohibited due to the increased risk of combustion and explosion. Oxygen supports combustion and, when combined with fuel gas, creates hazardous conditions that can lead to dangerous explosions if any leaks are present in the piping system.

In contrast, nitrogen, carbon dioxide, and air are generally considered safer options for testing purposes. Nitrogen, being an inert gas, does not react with typical fuel gases, making it an ideal choice for pressure testing gas piping systems. Similarly, carbon dioxide can be used without the same level of risk associated with oxygen. Air, while not the most common, is also acceptable in many scenarios as long as it is used with caution and within prescribed guidelines.

Therefore, the prohibition of using oxygen is based on safety regulations aimed at preventing incidents that could result from its reactive properties when dealing with fuel gases.