Formaldehyde is one of the most important indoor air pollutants affecting human immune system, and causing various respiratory diseases and even certain cancers. Traditional formaldehyde detection technologies are bulky, expensive and difficult to maintain. Here, we report a colorimetric chemical sensing platform for fast (2 min) and sensitive detection (30 ppbv) of formaldehyde over a wide dynamic range (0-750 ppbv). The sensor can tolerate humidity variation from 5% to 90% and is immune of common interferents, such as CO 2 (4%), SO 2 (10 ppm), NO 2 (125 ppbv), and O 3 (300 ppbv) in air. We also demonstrated continuous detection of formaldehyde on this sensing platform using disposable sensor chip.Index Terms-Colorimetric sensor, formaldehyde, gas sensor, indoor air quality.