This FY4150 Series replacement filter, integrated with Philips-exclusive NanoProtect Active Carbon technology, is a dedicated accessory tailored for Philips 4000i series air purifiers—specifically models AC3833, AC3836, and AC3837. As a core component that matches the high-performance standards of Philips 4000i series (known for smart air quality sensing and large-room coverage), it not only restores the air purifier’s original purification capability but also enhances the removal of gaseous pollutants and odours, creating a healthier, fresher indoor environment for families.