# Application Assessment of Electrical Cables during Smoldering and Flaming Combustion
## 3 Results and Discussion  
The A-F cable samples selected for testing were subjected to flaming and smoldering combustion processes initiated by a heating plate or by electric current flow through the copper wires. Changes in the extinction modulus and smoke concentration were examined for all tested cable samples. An exemplary graph of the extinction modulus (m) change as a function of time for cable A during smoldering combustion initiated by a heating field is shown in Figure 2.  
The A-F cable samples selected for testing were subjected to flaming and smoldering combustion processes initiated by a heating plate or by electric current flow through the copper wires. Changes in the extinction modulus and smoke concentration were examined for all tested cable samples. An exemplary graph of the extinction modulus m change as a  
Figure 2: Changes in the extinction modulus (m) as a function of time for cable A, smoldering combustion initiated by a heating field. function of time for cable A during smoldering combustion initiated by a heating field is shown in Figure 2.  
Based on the analysis of the results obtained for three tests, it can be concluded that the reproducibility of the measurements was at a satisfactory level. The results obtained for the average values of the extinction modulus (m) and the concentration of smoke (Y) are presented below. Changes in the mean extinction modulus (m) as a function of time for all cable samples in a smoldering combustion process initiated by a heating field or electrical current flow through wires and for flame combustion are shown in Figure 3a-c.  
Figure 3: _Cont._  
Based on the results obtained in the process of smoldering combustion initiated by the heating field, it can be seen that within 200 s after the heating of the heating plate, smoke particles reached the densitometer disposed on the ceiling. Among the tested samples, cable F, for which the combustion process began the latest, after about 650 s, was significantly different. For this cable, the value of the extinction modulus was the smallest out of all the cables. In addition, it was observed that the smoke generated by the smoldering combustion of cable F (which had a silicone sheath) was significantly different from that of the other cables (a delicate mist made up of small particles which could be seen with the unaided eye) and did not diffuse the densitometer light beam. On the other hand, the results obtained for the smoldering combustion initiated by the electrical current flow through the copper wires indicated clear differences in the course of this process compared to smoldering combustion initiated by a heating field. The value of the extinction modulus for cable C was measured only in the range of 100 to 200 s of test duration. After firing of the internal insulation through the heated wire of the cable, the value of the extinction modulus remained at the level of 0 dB/m. Moreover, the value of the extinction modulus for cable D for the duration of the test did not exceed 0.15 dB/m. The greatest extinction modulus value was measured for cable B with plasticized PVC insulation and sheath. Based on the analysis of the results obtained for the process of flaming combustion, it can be concluded that the value of the extinction modulus for cables C and F was at the background level due to the lack of large smoke particles. The resulting smoke looked like a fog, which should be measured by an ionization chamber. Moreover, flaming combustion of cable A started from the beginning of the test, while the increase in extinction modulus deviated from the results for the other cables, as it was slower and about 300 s later the maximum during the test was reached. This result was probably related to the type of halogen-free material used and the cable construction. Figure 3: (**a–c**) Changes in the mean extinction modulus (m) as a function of time for all cable samples in flaming and smoldering combustion processes. (**a**) Smoldering combustion process initiated by a heating field.