The fire that he had was really very destructive when he wanted it to be, so even though the fire that he could control was still just the size of a basketball, it was still very useful in killing zombies.
The fire that he had could burn things faster than the fire of others, and his fire also doesn't die down easily, so it would continue burning the zombies until he controlled it again.
They had tested it before, and without his control, the fire he had would continue burning for half a day without dying down no matter how small it is.
What's even more scary is that as long as there's something that could be burned around it, it would continue to spread for a long time because it doesn't die down easily.
So, even though Camille was using it to kill some zombies, he would always check it again if he had controlled the fire to die down afterwards.
Of course, the others were also checking it because it would be bad if it continued to spread without their knowledge.
