When PVC is burning during fire

it will produce a lot of HCI that is harmful to human beings．As the concentration of HCl is the main criterion of the HCl toxicity

it is important to detect the HCl concentration during the PVC fire A fire smoke releasing device and a Fourier transform infrared spectrometer (FTIR) were used to conduct a quantitative on-line analysis on the concentration of HCl in smokes of PVC in a burning process．The results showed that ahhough the concentration of HCl increased slightly when the PVC was on fire．PVC released most of HCl (about 80 percents) before that in the stage of thermal degradation

and the smoke toxicity reached a peak value The phenomena indicated that the release pattern of HCl is quite different from that of CO and CO2 So when the fire is caused by the combustion of PVC

it must be noticed that the worst case will happen before the flame occurs.