# Application Assessment of Electrical Cables during Smoldering and Flaming Combustion
## 3 Results and Discussion
### The Operation Times of the Detectors  
The following diagrams show the comparison of the operation times of the tested smoke detectors for smoldering and flaming combustion. The designation and type of detectors used are in accordance with Table 2. The average operation times of smoke detectors for cables during the smoldering combustion processes initiated by a heating plate or by electric current flow through the copper wires, as well as flaming combustions, are summarized in Figure 5.  
Figure 5: _Cont_. Figure 5: _Cont._  
Figure 5: _Cont_. On the basis of the obtained results, it can be stated that smoke detectors detected flaming combustion products more quickly than smoldering combustion products due to a higher temperature increase during combustion and the smoke particles reaching the detectors faster. In addition, for cable C, only detector 6 was activated due to the very small smoke particles generated during the combustion process. The optical detectors react faster to an increase in smoke concentration (Y) than the extinction modulus (m), e.g., cable F. It should be emphasized that fire detectors, for smaller values of extinction modulus (m), need more time to act. Linear detector 2, which was placed lowest in the chamber, did not detect a fire during 1000 s of test duration and for cable F did not work in any of the tests. The smoke detectors 1 and 6 detected fire in the shortest times, and, in addition, detector no. 6 was the only one that worked for all fires in time up to 1000 s.  
The response times for the two linear detectors are shown in Figure 6.  
The graphs show the time at which the smoke filled the test chamber during smoldering combustion initiated by a heating field or initiated by electric current flow and flaming combustion. On the basis of the obtained results, it was found that, for cables C and H, during the smoldering combustion initiated by a heating field, smoke filled the chamber's space at the lowest level for all the detectors in the shortest time (C-300 s and H-400 s), while, for the smoldering combustion initiated by the flow of electric current through wires, the chamber was filled with smoke in the case of cable B. Detector no. 2 was activated after 680 s. During the flaming combustion, the shortest time of filling of the chamber space to a height of 1.8 m was measured during the test with cable I (64 s). The average changes in CO concentration as a function of time for the analyzed types of combustion are presented below. The average values were determined as the arithmetic means of three measurements for the same type of cable. Such a number of measurements eliminates measurement errors and allows for averaging. Figure 7a-c show graphs for the concentration of CO for all cable samples as a result of smoldering combustion initiated by a heating field or by the flow of electric current through wires and for flaming combustion for each type of cable. Figure 5: The average operation times of smoke detectors 1–6 for cables during smoldering and flaming combustions. Figure 6: _Cont._  
Figure 6: The response times for the two linear detectors during smoldering and flaming combustion. Figure 7: _Cont._  
Based on the analysis of the smoldering combustion results initiated by a heating field, it can be concluded that the CO evolution began at about 240 s, and the maximum CO concentration value was measured for cable H, while, during the smoldering combustion initiated by the flow of electric current through the wires, cable C began to burn from the inside before the others, which can be seen in the m and Y curve charts (Figures 3b and 4b). The maximum CO concentration value was measured for cable A. In the process of flaming combustion, CO production started about 50-100 s from the start of the test, and the maximum CO concentrations were twice as large compared to the values obtained during the smoldering combustion. In summary, it can be concluded that, for cables burned in the flaming combustion process, CO concentration values were the highest.