When a flammable gas leak from a pressurized cylinder or tanker valve catches fire and is burning as a torch flame, what is the fundamental firefighting rule under JT/T 617.6 and fire rescue doctrine?

1. Do NOT extinguish the flame unless the gas source can be safely and immediately shut off; unignited escaping gas will form a massive unconfined explosive vapor cloud
2. Extinguish the flame immediately with a fire blanket and let the unburned gas flood the highway
3. Pour sugar water over the flame to convert the gas into solid caramel
4. Throw rocks at the valve to snap it off completely