The global burden of smoking-related diseases is substantial, with over 7 million deaths annually. Tobacco smoke is an aerosol composed of more than 3800 individual compounds, volatile agents in vapor phase and nonvolatiles in the particulate phase. The majority of toxic and carcinogenic compounds are in the tar a nicotine-free dry particulate matter. The most important and conventional approach to reduce harmful compounds is using fibrous filters as filter tip. Nano-fibrous membranes due to their irregular internal structure, inter-connected pore, sub-micron pore size, high porosity and specific surface area are considered to be one the most effective means in general pollution control. One of the most important features of these filters is ability to engineer them. Factors such as fiber diameter and orientation distribution as well as porosity, pore size and thickness can assist to the design. These parameters affect air permeability and filtration efficiency of nano-fibrous membranes. The structure of nano-fibrous membranes is a function of various processing parameters such as applied voltage, feed rate, collector speed and solution concentration. In order to investigate the effect of processing parameters on air permeability and filtration efficiency of the filter, polyurethane electrospun nanofibrous membranes were produced under different applied voltage, feed rate and solution concentration. Afterwards, the FESEM images of membranes were obtained. The surface porosity of the structure, fiber diameter and orientation distribution as well as 2D pore size distribution of membranes were obtained using image analysis techniques. Thickness and air permeability of membranes were exprimentally measured. Filtration efficiency of membranes was assesd using a developed setup. The effect of processing parameters on fiber diameter and orientation, pore size distribution, porosity, air permeability and filtration efficiency of structures was investigated. A Matlab-based program capable of producing ?brous structures with various ?ber diameters, porosities, thicknesses and 3D fiber orientations was developed. The obtained parameters from FESEM images were then implemented into the simulation code to generate 3D virtual nanofibrous structures. 3D pore size distribution of 3D imgaes was then calculated using a novel image analysis technique in Avizo software. The results indicated that polymer concentration, applied voltage and feeding rate affect fiber diameter, pore size, surface porosity and air permeability of membranes. Increasing polymer concentration fiber diameter, pore size and air permeability increase while filtration efficiency decreases. It was also found that with increasing the applied voltage, fiber diameter, pore size and air permeability reduces and filtration efficiency increases. Increasing the feeding rate results in formation of coarser fibers and larger pore size and hence higher air permeability and lower filtration efficiency. It was also established that, fiber orientation does not significantly affect filtration efficiency. The results showed that 3D pore size calculated using image analysis of virtual structures is larger than 2D pore size calculated using image analysis of FESEM images.