Demonstration abstract: PiMi air box — A cost-effective sensor for participatory indoor quality monitoring

Ultra-fine particles with aerodynamic diameter smaller than 2.5 microns, namely Particulate Matter 2.5 (PM 2.5), are capable of penetrating the lung cells and circulating the circulatory system, and compose a major health threat to people. Although the government is publishing the outdoor PM2.5 concentration on an hourly basis, the indoor PM 2.5 concentration, to which most people expose for most of their everyday life time, remains unsupervised. The high cost of the professional PM 2.5 measuring equipments, which utilize filtering and direct mass measuring methodology, prevents the indoor air quality to be monitored pervasively. We designed and implemented PiMi air box, a cost-effective portable sensor, which is able to estimate the PM 2.5 mass concentration with satisfactory accuracy. The PiMi air boxes adopt the low-cost optical particle counting technology and convert the particle counts into PM 2.5 mass concentration via empirical diameter-distribution and density of particulate matters. The errors introduced by the individuality of the low-cost particle counters are offset during a machine-learning-based calibration procedure for each single unit. The PiMi air box enjoys a stunning cost reduction by a factor of 1,000 comparing to professional equipments, and still maintains an satisfactory level of accuracy for everyday life air quality measurement. Together with embedded Bluetooth connectivity and SmartPhone APPs, PiMi air box is well-suited for massive crowd-sourced indoor air-quality monitoring research.