| More attention has been paying to the indoor air monitoring as for heavily increasing indoor air pollution nowdays. This paper combines practical monitoring working and according to the GB50325-2001 "Code for indoor environmental pollution control of civil building engineering " and the GB/T18883-2002 " Indoor air quantity standard" , we improved the analyse condition and made a equip that could keep sampling tube in a low temperature and a dehydrating unit made up of low temperature glass bead. We can obtain precise analytical data of benzene and TVOC at the same time from one sampling and one analysis by the sampling requirement in this paper. The preparation of VOCs liquid CRMs and the optimum conditions of making the preference tube of VOCs was studied.The standard methods of thermal desorption/capillary gas chromatography order the sampling flow as 0.5L/min, the sampling time as 20min, and has no order about the sampling temperature. But experiments evidence that the temperature of Tenax tube, sampling flow and sampling time has significant effects on the recovery ratio of BTEX and other VOCs.We found that the humidity has great impact on the recovery ratio by more experiments. The recovery ratio of benze cannot approve to 90% when only control the temperature of Tenax tube. Furthermore, when sampled at low temperature, the FID detector often flameout. We increase a tube filled with low temperature glass bead in front of Tenax tube to dehumidify; by this we get a good result and resolve... |
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