# Assessing Crisis Management Tools for Sustainability of Industrial Safety
## 4 Model Situation  
For a model situation, a year-round skating arena was chosen, in the city centre, which serves the local population for sports events. Its capacity is 1619 seats, and the dimensions of the ice surface are 61 \(\times\) 26 metres. According to the scenario of the IRS units, aimed at practicing the leakage of a hazardous substance, there was a malfunction of the cooling equipment in the engine room of the aforementioned skating arena and a subsequent ammonia leak.  
The cooling system of the skating arena consists of an engine room and a closed ammonia cooling circuit. The cooling engine room is located next to the skating arena area in a new separate building, from where there is a channel for the skating arena piping.  
The monitoring system for detecting ammonia leaks in the cooling plant relies on a set of sensors. The sensors are integrated into a monitoring system that constantly monitors ammonia \(C\) (_H1_, _H2_, and _H3_). These sensors are designed to detect specific thresholds of ammonia \(C\), which trigger various safety mechanisms depending on the severity of the leak.  
The stated values of 60 ppm (_H1_) and 120 ppm (_H2_) were chosen based on internationally recognised standards for detecting and managing ammonia leaks in industrial facilities. These limits are defined to trigger preventive measures. At a \(C\) of 60 ppm (_H1_), optical signals and ventilation are activated to minimise the risk of further \(C\) increases. At 120 ppm (_H2_), compressors are additionally shut down, and acoustic signals are trig gered to prevent ammonia levels from reaching even more dangerous thresholds. These thresholds are crucial for timely warnings and the protection of public health.  
Table 1 specifies, in more detail, the provision of warning and notification in the event of an extraordinary event associated with an ammonia leak at a skating arena. If the ammonia leak reaches an emergency state, the \(H3\) signalling is triggered, and the civil protection siren is activated. In the process of emergency ventilation, there is extraction from the cooling plant and from the distribution channel. Here, however, it is desirable to proceed to measurements of the \(C\) of ammonia in the vicinity of the cooling plant and in the building of the skating arena, together with the monitoring of ammonia vapours.  
Emergency leakage of partial amounts of ammonia in these conditions poses a major risk to the population around the skating arena. Accidental leakage of ammonia most often occurs due to a malfunction of the safety valve on the ammonia circuit or due to the loss of integrity of this circuit. Most ammonia is in a liquid state under the given conditions at a pressure of 0.2-1.35 MPa. Its low boiling point (\(-33\)\({}^{\circ}\)C) at atmospheric pressure causes an intense boil in an emergency leak, leading to the formation of a gaseous cloud of ammonia. In the evaluation and calculations, the analysis of the spread and dispersion of ammonia in the area with civilian amenities, especially in the vicinity of the skating arena, was crucial.  
In areas with cooling equipment that uses NH\({}_{3}\) refrigerant, ventilation in accordance with STN EN 378 is observed. Ventilation is provided by a mechanical ventilation fan. The engine room is equipped with emergency ventilation, which changes the air at least 15 times per hour through the air conditioning ducts.