PVC Sheathed Electrical Cable Fire Smoke Toxicity

The cone calorimeter, under free and restricted ventilation conditions, was used to investigate the toxic emissions from PVC cable fires. Toxic gases were measured using direct high temperature gas sampling from the exit of the cone calorimeter with a short chimney attached to the exit from the electrical cone. Toxic species CO and HCl were identified as a function of time using a heated Gasmet FTIR. The particle number was determined using the Cambustion DMS500 fast response particle sizer with a diluted sample taken from the diluted cone calorimeter exhaust flow at the same location as the optical obscuration smoke meter. The HCl concentrations from the Chlorine in the PVC sheath demonstrated HCl levels well above the LC50 concentration for HCl. The restricted ventilation reduced the peak fire heat release rate and the peak toxicity and HCl occurred later than for free ventilation. The equivalence ratio in the gases from the combustion zone, were both rich at 1.5 for free ventilation and 1.3-1.4 for restricted ventilation. The toxicity results showed the classic phases of compartment fires: growth, steady state burning and then fire decay. After flaming combustion was extinguished, slow char combustion continued with high CO emissions. The particle size distribution showed peak particle number, PN, nuclei mode particles at 10 nm and an accumulation mode at 100 nm. The number of particles at 10 nm for free and restricted ventilation were extremely high and showed that the freely ventilated fires had the highest PN, but later in the fire the restricted ventilation PN were higher. Nano-particle emissions < 50 nm from PVC fires are a health hazard that is currently unrecognized and unregulated.