Design and implement of air quality monitoring system with two-stage IIR filter

Increasing attention has been paid to air quality monitoring with the development of the industry, and indoor air quality (IAQ) may increase the concentration of harmful substances like carbon monoxide (CO), nitrogen dioxide (NO2) in the air, which could increase the possibility of the respiratory and cardiovascular diseases. In this paper, the portable and cost-effective monitoring device is designed to detect the concentration of the harmful gas. With this device, the realtime concentration curve is plotted, and the two-stage IIR filter is designed to decrease the potential interference. The results show that the SNR is higher than that without filer in five different gas and meanwhile concentration curve has less burr and is clearer.