Introduction: The most important goal of modeling is to acquire knowledge about the real system's behavior. Toxic leakage in process and chemical industries is likely to be one of the main causes of working people and residents around these industries.

Method: In this study, the ammonia liquid release from storage reservoir in one of the southern refineries was investigated and analyzed using of ALOHA software. This research was modeled on three scenarios: 1. modeling the formation of toxic vapor clouds 2. Modeling the flammable environment 3. Modeling the toxic explosive atmosphere.

Results: Based on the results of this modeling, the concentration of ammonia is 1100, 5 km around the reservoir (red range). The area around the reservoir (orange range) is about 160 miles (about 10 km) from the area. In the event of full leakage of ammonia from the reservoir up to 500 m, the ammonia concentration is about 90000, which is about 60% of the minimum flammable concentration of ammonia gas and up to about 1.7 km of the ammonia concentration tank of 15000, which is about 10% of the minimum flammable gas concentration Ammonia. In the event of a supersonic explosion, the explosive wave pressure is approximately 700 meters from the reservoir equivalent to Psi 8, which can cause serious damage to the buildings.
Conclusion: According to the results of modeling, ammonia toxicity is the most important threat to personnel. Therefore, inspections in accordance with the company's proposal on ammonia repositories and emergency response plans will have an effective role in limiting the harmful effects of toxic and dangerous emissions.