Fire Safety Science Digital Archive

Experiments in which PVC wire insulation was decomposed by an electrical overload in a plenum or in a 200 k PMMA box showed that the highest concentration of HCl in the atmosphere was always less than 40% of the theoretical amount of chlorine in the original sample. Furthermore. This concentration quickly decays to a level that is dependent on humidity, but never more than 4% of the theoretical maximum. A mathematical model was used to determine a number of parameters that describe the system. The same model applies to both large and small scale tests. This treatment showed that less than 48% of the chlorine in the wire reached the atmosphere. It also showed that the rate of decay was primarily dependent on the rate of transport in the system, producing a half life of 5-6 min without external agitation. Furthermore, the final HC1 concentration was found to be dependent on relative humidity, and on surface composition (painted gypsum or PMMA).