# Mine Fire Behavior under Different Ventilation Conditions: Real-Scale Tests and CFD Modeling
## 3 Results and Discussion
### Experimental Data
This phenomenon is due to a natural pull of the ventilation in the same direction of the flow due to a temperature increase once the fire reaches its maximum development. Then, as the fire loses power, the additional airflow is gradually reduced until it reaches the initial situation. In addition, it was also observed that it acted as a resistance during a brief period of time at an early stage of the fire, reducing the airflow. In the case of pollutants generated by the fire, scenarios E1 and E2 followed a similar trend, while scenarios E3 to E5 had a different common pattern. In the first case, there was a reduction in oxygen as a consequence of a very important increase in the concentrations of CO, NOx, SO\({}_{2}\), and CO\({}_{2}\) 900 and 1650 s after the start of the fire for trials E1 and E2, respectively. This difference is mainly given by the airflow variation in the intake. In the E1 test, the airflow was very low, 1.93 m\({}^{3}\)/s, increasing the pollutants due to incomplete combustion in an earlier stage. In the case of E2, as the airflow was higher, 5.1 m\({}^{3}\)/s, the incomplete combustion phenomenon appeared once the fire was fully developed. On the other hand, trials E3, E4, and E5 showed a common behavior, increasing the concentration of pollutants once the fire reached its maximum power, with a stable emission period and finally decreasing the concentration as the fire faded. The only difference between scenarios was the pollutant concentration, showing a direct relationship with the fuel load, and the time to reach the maximum level of emissions (1080, 480, and 450 s, respectively). Figure 8: EvolutioSn of the environmental conditions over time; test 4. Figure 9: Evolution of the environmental conditions over time; test 5. The temperature evolution displayed a similar trend: a rise in temperature followed by a stable period of maximum temperature and then a progressive decrease as the fire faded. However, there was an important divergence if it was compared the period from which the temperature increased because of the fire. The temperature increase was recorded earlier than pollutants in E1 and E2, while, in E3 and E4, the opposite occurred and E5 showed an almost identical start for temperature and pollutants. On the other hand, a phenomenon already mentioned in the previous figures was observed upon analyzing the behavior of the flow. Shortly after reaching the maximum fire power, there was a decrease in the temperature until it reached a stable level. This was due to the fire acting as a resistance in the ventilation circuit at the beginning, as can be seen in the sensors close to the fire: S2, S3, and S4. This phenomenon indicates that there was an advance of the fumes in the opposite direction of the flow during this period, i.e., a roll-back [8], being more pronounced in the case of lower initial airflow. Regarding the maximum temperatures reached, there was a notable difference between lower and upper parts of the drift, showing a 60-320% difference in temperature for the same cross-section. The outcomes obtained are very important to know potential hazardous scenarios in drifts from the production level, with similar sections and airflows, and where an important quantity of equipment is placed. The knowledge of temperatures and pollutant concentration over time can be used to apply safety and corrective measures.