Indoor VOCs Multicomponent Photoionization Detection

The World Health Organization pointed out in the relevant report on factors affecting human health that environmental factors account for 17%,biological factors account for 15%,and medical service factors account for only 8%.Among them,air quality plays a decisive role in environmental factors,especially indoor volatile organic compounds（VOCs）directly affect human health.Therefore,the detection of indoor VOCs has very important practical significance.In this thesis,a new indoor VOCs detection instrument is developed to realize the online and real-time detection of the concentration of each component of indoor VOCs mixture gas,so as to detect the concentration of relevant components harmful to human body more finely.（1）According to the multi-component characteristics of indoor VOCs,the principle of gas chromatography is proposed to separate the mixed gas in time sequence.In the detection method,the photoionization sensor is used to measure the time sequence information of the separated gas,which solves the problem that the indoor VOCs can not be identified.（2）Starting from the tray theory of gas chromatography,the theoretical study on the outflow curve of chromatographic column was carried out.The concentration model of mixed gas flowing out after chromatographic column separation is established,the detection principle of photoionization detector is deeply studied,and the detection characteristics of photoionization sensor are analyzed,which provides a theoretical basis for the construction of the whole system.（3）On the basis of theoretical methods and key research,the overall scheme of indoor VOCs detection system is determined,and the experimental platform for indoor VOCs detection system is developed and completed.The platform includes gas path unit,separation unit,detection unit,control unit and data acquisition and processing.The construction process of hardware and software of the whole VOCs detection system is described in detail.（4）Aiming at the problem of low signal-to-noise ratio of the collected signals in the VOCs detection system,a denoising algorithm combining variable modal decomposition（VMD）and energy entropy（EE）for indoor multi-component photoionization detection is constructed.This denoising method is compared with EMD and wavelet denoising methods,and the results show the superiority of this method in this system.