Air pollution remains a critical global concern, contributing to environmental degradation and posing serious health risks due to the widespread presence of particulate matter, volatile organic compounds (VOCs), and microbial contaminants. Conventional filtration systems often face limitations in efficiency, sustainability, and adaptability, highlighting the urgent need for advanced, eco-friendly alternatives. This chapter explores the innovative application of bio-aerogels as promising nanostructured materials for air filtration, emphasizing their high porosity, low density, tunable surface chemistry, and biodegradability. Derived from renewable sources such as nanocellulose, chitosan, and carbon-based biopolymers, bio-aerogels are categorized and evaluated based on their unique performance characteristics. The chapter also details green fabrication techniques including sol-gel processing, freeze-drying, and functionalization that support scalable and environmentally responsible production. Core air filtration mechanisms such as particulate matter interception, VOC adsorption, antimicrobial activity, and catalytic degradation are thoroughly examined, alongside real-world applications in industrial air purification, indoor air quality enhancement, personal protective equipment, and automotive systems. A comparative analysis with conventional filtration media is presented, highlighting the superior efficiency, durability, and multifunctionality of bio-aerogels, while addressing current challenges and future research directions that support their integration into next-generation sustainable filtration technologies.