I have always wondered what they are made from.
The only real way to remain safe during a bush fire is Distance. Get as far away from the fire. You can have as many contingency plans to combat the fire but if decide to stay and fight it like many that perished on Hells Weekend you place yourself at the mercy of the demon. Ask any fireman in the business, even they would have evacuated on that terrible day. Fires take on a life of their own, unpredicatable and deadly. Why did so many stay and attempt to fight the fires? CFA recommendation? no insurance? Beaten fires before? no one knows but whatever the answers are, they werent worth the lives that were lost
I would say the base because that's where the fire is built from.
Base of the fire unless it is a liquid fire. Then you should try to smother it. Aiming at the base of a liquid fire will only spread it.
The textbook answer is at the base. Best practice is to start high and then go lower once the powder has reached the flames. As someone else said don't use water on electrical nor should you use it to chase a grease fire! Place your extinguishers near an exit and use them only when you can safely fight the fire. ALWAYS have your back to the exit so you can turn and leave when the extinguisher is nearing empty.
Base of the fire - the fuel source.
