## 1 Introduction  
In many applications, air filters contribute to protect components which are sensitive to contaminants, such as carbon monoxide, sulfur containing compounds, salt aerosols, hydrocarbons, ammonia, and nitrogen oxides. As shown in the literature [1,2], the best method to deal with air contamination of an energy production system is by using an air filter [2]. It is well known that filters must be designed to be durable and effective, maintain a low pressure drop, have a long lifetime, be easy to handle, be low cost, have a small package space, and be flexible to each specific demand. Nanofibers are one of the unique materials which have many advantages applicable for manufacturing air filters in order to respond to specific requirements as listed above due to the high surface-to-volume ratio, low resistance, and enhanced filtration performance. Recently, scientific techniques, along with nanotechnologies, have increased interest in methods capable of producing fibers that are produced from nanometers to micrometers [3]. Electrospinning is a manufacturing process that utilizes a different electric charge [3,4]. Polymers, ceramics, composite materials, a solution, or a molten material are able to produce fibers with a diameter from micrometers to nanometers with a relatively simple method [5]. Nanofibers produced by electrospinning have a high filtration efficiency for their very small diameters, large surface area per unit mass, and small pore size [6]. Additionally, due to the large porosity, the pressure drop that occurs is low when filtering impurities. Using these characteristics, submicron size particles or harmful gases can be removed. The nanofiber air filter can be used in various places, such as in semiconductor, clean room, dust collector, power generation, and precision machinery applications [7, 8, 9]. For the fabrication of polymer nanofibers, electrospinning has been recognized as an efficient technique. Electrospinning is achieved when a high voltage is applied to the water droplets hanging on the edge of the capillary. It has been known worldwide that the electrospinningning method uses an electrostatic field and ejects to liquid jet from the syringe tip [10; 11; 12]. The hemispherical shape of the suspended droplet preserved in equilibrium at the end of the syringe tip may be distorted into a cone in the presence of an electric field. Surface tension is reduced with the electric charge distribution induced on the surface of the liquid, causing a distortion in the balance of the repulsive force. When the jet exceeds a critical voltage, a stable jet of liquid is ejected from the syringe tip. In the case of a low viscosity liquid, the jet is broken up into droplets as a result of the longitudinal Rayleigh instability caused by the surface tension. Conversely, for high viscosity liquids, the jet does not break up; however, it travels continuously to the collector plate. A transverse instability or splaying of the jet into two or more smaller jets is observed due to the radical charge repulsion [13]. This process is termed as electrospinningning and it products the polymer fibers with a diameter in the nanoscale [14; 15; 16; 17; 18; 19]. It is well known that polyacrylamide(PAN) materials have attracted much attention because of various excellent characteristics, such as thermal stability and tolerance to most solvents, atmosphere, bacteria, and photo irradiation, making them suitable for air filter applications. In this research, we conducted the electrospinningning using a PAN polymer with a dimethyl formamide (DMF) solution to produce nanofibers, which can be potentially-applied cathode air filters. In addition, the PAN nanofiber air filter, which was fabricated by using the electrospinningning method and laminated by non-woven fabric and PAN nanofiber through a heat roller, was experimentally analyzed for the filtration efficiency and pressure drop.