Which of the following is not a potential source of ignition for propane?

Propane is a highly flammable gas, and understanding its potential sources of ignition is crucial for safety. In this context, the correct answer identifies wood as not being a direct source of ignition for propane. While wood can catch fire and contribute to a larger fire, it does not ignite propane gas on its own.

On the other hand, fans can create sparks or heat, making them a potential source of ignition. Electrical switches can create arcing that ignites flammable gases like propane. Cigarettes are also a well-known source of ignition, as their burning embers can easily ignite propane vapors.

Thus, wood, although it can burn, does not serve as an immediate ignition source for propane, making it distinct from the other options provided. Understanding the nuances of ignition sources is essential for maintaining safety in environments where propane is present.