GC usually was used to measure and control the ratio of HAPs exactly by peak area normalization method. The original column and six-injection valve installed to GC-8A gas chromatog. for the detection HAPs were installed to GC-14B, and the abnormal conditions appeared after the chromatog. conditions being set. The "bifurcate peaks" phenomenon of one-component during HAPs anal. was a fake fault caused by improper instrument configuration and material selection making glass insert, opening loop and vaporizing chamber form special structure and using the six-injection valve simultaneously. It was suggested that the stainless steel opening-loop should be replaced with flexible materials resistant to high temperature and the length of glass insert should be extended appropriately.