This is about as good of an example of how a flammable gas(s), such as propane, are MORE dangerous away from the leak point. As you can see in this video, the leak is occurring in the top right corner of the frame and the ignition occurs off-screen to the top left and flashes back to the source. Also take note of how the vapor in the bottom half of the frame slowly burns off after ignition. This occurred at a fueling station and a vehicle caused the initial damage which led to the leak.