how can I detect one our more helmet safety for workers?

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Hi everybody, my name is Wilian Pasternak and I´m Brazilian. So, I must detect one our more helmet safety for workers in a building. I have been trying to use HaarTraining, but not get a good result. Somebody can help me with tips how make do this? I think to use SurfDetector, but not try yet this way!.

Sorry by my english!!!