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The objective of this work was to investigate preliminary design criteria of automatic fire alarm systems for some places with high flow velocity, e.g., exits of large underground car parks, the air outlets of large air conditioner etc. In addition, another main motivation of this research is to evaluate the appropriateness of Chinese standard which states that photoelectrics should be used in high flow locations. Two corresponding series of experiments were designed to analyze the response sensitivity of photoelectric and ionization smoke detectors under the conditions of different flow velocities in the Fire Emulator/Detector Evaluator (FE/DE), using smoldering cottons as the smoke source. The combining analysis of results of the two series of experiments indicated that generally speaking, ionization smoke detectors showed better response sensitivity than photoelectric smoke detectors in environments with high flow velocity. Preliminary analysis suggested that the influence of flow velocity on size distribution of the smoke particles generated is the main reason for the results.