When we talk about fire it is important to know that...
1. Fire grows exponentially.
2. In minutes a fire will become so big that you will need thousands of Ltrs/KGs of extinguishing agent to put it out.
3. The first few minutes are all you have got to do something. After that golden period all you can do is pray that Fire Brigade could get there before everything burns down.
If you detect a fire in its incipient stage it would be easier to put out as it would have not grown to a blaze stage.
One can go close to the fire & use a hand held portable extinguisher. This would not be possible if you detect the fire in its blaze stage.
That is why when it comes to fire fighting early detection is the key.