Which method is considered unacceptable for checking a propane piping system for leaks?

The use of a flame is considered an unacceptable method for checking a propane piping system for leaks due to the inherent dangers involved. Propane is a highly flammable gas, and introducing an open flame could ignite any escaped gas, potentially leading to explosions or serious fire hazards.

In safety practices, leak detection should focus on non-combustible methods that can effectively identify gas leakage without introducing additional risk. Other methods, such as using a pressure gauge, applying a soap solution, or performing a visual inspection, are safe and effective. By measuring pressure or applying a soap solution to detect bubbles forming at leak points, you can identify issues without risking ignition from a flame. Visual inspections also play a critical role in identifying physical damage or flaws without any safety implications.