Electronic nose (e-nose) is a sensing device that can detect and recognize various odors or gases in the environment. E-nose technology has various applications in different fields, including quality control, food safety, and medical diagnosis. Signal processing plays a crucial role in improving the performance and accuracy of e-nose devices. The signal processing techniques include feature extraction, pattern recognition, machine learning, data fusion, and statistical analysis. Various signal processing techniques such as artificial neural networks (ANN), support vector machines (SVM), principal component analysis (PCA), independent component analysis (ICA), wavelet analysis, Fourier analysis, and time-frequency analysis have been used for e-nose applications. These techniques help in identifying the odor and gases present in the environment and classifying them based on their chemical composition. E-nose can thus be used as a cost-effective and portable tool for odor identification, quality control, and safety assurance in different fields.