I don't agree with white or black smoke meaning one is a fire and the other is only need for caution. Many wheels are made of magnesium, and when they start fire, they don't give off black smoke. Nor is it easy to put out. I feel that anyone who simplifies this to black smoke for fire and white smoke for caution shouldn't be around A/C. They obviously don't pay enough attention to the real cause of the problem. I think before the pilot evacuated the cabin, he should have made a more accurate assesment of the problem. But having said that, I was not there, and don't know the whole story.