'kleaan.' is an anti-pollution mask that filters the harmful particles most commonly found in urbanized areas. It has been designed using advanced 3D modeling tools as well as digital fabrication techniques, and uses certified filters, making it one of the most comfortable and effective pollution masks on the market. At the same time, 'kleaan.' masks can be integrated with multiple Internet of Things sensors that are provided separately, making it the first wearable device that is truly customizable. Users can choose the sensors and metrics they want to track, including conventional biometrics (steps, distance, heart rate, etc.) as well as advanced metrics unavailable from most wearables (pollution level, breathing rate, stress level, etc.). With the help of its smartphone application, 'kleaan.' users can obtain information based on crowd-sourced data.