Formaldehyde is found in furniture and prefabricated parts and is considered to be harmful to health. The Philips Air Purifier AC3998 is equipped with a formaldehyde sensor to effectively remove this gas from indoor air. By means of a 24-hour progress chart, users can see how formaldehyde removal has progressed. The air purifier has a sleek design and conveys accessibility and friendliness with its fabric panel along the front.