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In order to develop large power transmission line, always passing through desert, it is necessary to know the breakdown performance of air gaps subjected to sand storm with different speed, sand size and sand concentration. In Saudi Arabia, the transmission lines are often subjected to the Sandstorm desert. This can lead to serious reduction in insulator effectiveness, resulting in flashovers and outages of electricity supply. In This paper, the breakdown characteristics of weakly and extremely non uniform field with dust particles in atmospheric air are investigated experimentally to provide fundamental parameters determining the breakdown voltage in desert condition around DC and AC power apparatus by air insulation. The effects of filed uniformity, air speed, dust size, concentration of dust particles are investigated. Experimental results show that the dust particle with large size has no effect on the breakdown voltage. On the contrary, the dust particle with small size causes a reduction on the breakdown voltage this reduction are due to the dust layer deposit on the electrode surface. Furthermore, the amount of reduction of breakdown voltage increases with the increase of air speed. Moreover, a numerical study to the effect of dust storm in electric field distribution along the gap axis between two electrodes has been calculated by a developed program using Finite element method. The simulated results were in a good agreement with the experimental findings and indicate that there is enhancement of electric field and it is distorted along the gap, it increases at some place and decrease at another place on the gap.