# Assessing Crisis Management Tools for Sustainability of Industrial Safety
## 4 Model Situation
### Results of Models of Individual Scenarios
#### 4.1.1 Scenario 1.1.  
Ammonia Leak under Stable Atmospheric Conditions  
In this scenario, an ammonia leak was simulated using ALOHA 5.4.7, incorporating critical geographical data (GPS: 49.135727, 20.433323) alongside atmospheric variables typical of summer conditions. With a low wind speed of \(v=1\) m.s\({}^{-1}\) and a temperature of \(t=25\)\({}^{\circ}\)C, the model accounted for the slower dispersion of ammonia, concentrating the gas near the source. The chemical properties of ammonia, specifically its molecular weight of 17.03 g.mol\({}^{-1}\), were essential in predicting the potential hazard zones.  
By integrating these data into ALOHA, the software utilised the Emergency Response Planning Guidelines (ERPG) to delineate risk zones based on ammonia concentrations at various locations over time. Under stable conditions, the simulation identified three distinct danger zones, each defined by specific concentration thresholds and associated health risks:  
* ERPG-1 zone (25 ppm \(\leq\) C(\(x\),\(y\),\(t\)) \(<\) 150 ppm) involves exposure that may cause mild irritation but poses no serious health risks (yellow zone in Figure 2).
* ERPG-2 zone (150 ppm \(\leq\) C(\(x\),\(y\),\(t\)) \(<\) 750 ppm) presents significant health risks, requiring immediate protective actions (orange zone in Figure 2).
* ERPG-3 zone (C(\(x\),\(y\),\(t\)) \(\geq\) 750 ppm) represents the highest concentration of 1500 ppm, where exposure can lead to serious health risks. Prolonged exposure may cause severe respiratory issues, requiring immediate intervention to prevent life-threatening conditions (red zone in Figure 2).  
**Scheme 1.** ALOHA, danger zones for Scenario 1.1. Note: The colour scheme identifies hazard zones with yellow for ERPG-1 (low risk), orange for ERPG-2 (moderate risk), and red for ERPG-3 (high risk), showing the spatial distribution of ammonia concentration levels and corresponding risk levels.  
The model identified that under calm conditions (\(v\) = 1 m.s\({}^{-1}\)), the ERPG-3 zone extended approximately 110 m from the source. However, this changed significantly under increased wind speeds (\(v\) = 5 m.s\({}^{-1}\)), as the hazard zone expanded to over 450 m for ERPG-2. This highlights how meteorological variables, such as wind speed, dramatically influence the extent of hazardous zones, underscoring the importance of incorporating real-time environmental data during emergencies.  
In Scheme 1, a simplified schematic of the ammonia dispersion pattern is presented, showing the concentration levels as a function of distance and wind direction. The dashed lines represent wind direction confidence intervals, which account for variability in meteorological conditions that could affect the spread of the gas.  
Table 2 summarises the numerical data for each danger zone under different wind conditions.  
These data, visualised through integration into Google Earth (Figure 2), assist emergency planners by providing spatially precise predictions of the affected areas.  
\begin{table}
\begin{tabular}{l l l l} \hline \multirow{2}{*}{**Danger Zone**} & \multirow{2}{*}{**Concentration Level**} & \multicolumn{2}{l}{**Equivalent**} \\  & & **Concentration** & **Range (m)** \\  & & **(mg.m\({}^{-3}\))** & \\ \hline ERPG-2 & 180 & 104.94 & 111 \\ ERPG-2 & 150 & 104.479 & 362 \\ ERPG-1 & 25 & 17.413 & 895 \\ \hline \end{tabular} Note: Colour coding used for hazard zones—yellow (ERPG-1, low risk), orange (ERPG-2, moderate risk), and red (ERPG-3, high risk), reflects increasing levels of risk due to ammonia concentration.  
\end{table}
Table 2: Danger zones for the NH\({}_{3}\) leak scenario at the skating arena, Scenario 1.1.  
Figure 2: A model determining vulnerability and risks for the affected area, due to the NH\({}_{3}\) leak (export of data from Scheme 1 to Google Earth for Scenario 1.1).