The base smoke density of the smoke fire detectors created by the air-pollutant inducing suspended particulate, especially the PM₁₀, has been analyzed. It has also been calculated according to the ionization fire detectors. Through the comparison of the differences of the base smoke density, induced by the different levels of particulate pollution in atmosphere in different areas, it was found that the difference in base affection is quite little. In this case, it is impossible that the sensitivity and false alarm ratio of the smoke fire detectors will increase when they work in the heavy air pollutant area. So, the standards to define the sensitivity of the smoke fire detector could be the same in different areas, which have different levels of air pollutant. In the future, the effect of the base smoke density would not be neglected with the development of the way to measure smoke with high distinguishability, such as the particulate counter.