针对近几年我国液氨事故频发情况，尝试通过危险与可操作性分析（HAZOP）和保护层分析（LOPA），揭示涉氨企业保护措施存在的不足，并以本质安全为目的提出保护措施。并建议将氨浓度≥ 30 mg/m³的所有区域划归氨泄漏最小隔离区。研究结果表明，当保护措施不足时，事故风险不可接受，为高风险；当采取保护措施后，可以将事故风险降到可容忍目标；当保护措施有效时，最小隔离区域划分在企业范围内。对于露天液氨储液器和氨冷冻隧道，建议通过在特制的液氨厂房或隔离设施内设置氨报警仪、抽风罩和水雾喷淋等装置，将氨泄漏危害控制在特制的液氨厂房或隔离设施内。

In recent years,accidents related to liquid ammonia happened more frequently in China.Both HAZOP and LOPA methods are utilized to reveal the existed deficiencies in protection measures adopted by ammonia-related enterprises that locate at cities in China.The corresponding protective measures are put forward for the purpose of essential safety.In addition,all the areas in which the concentration of ammonia is higher than 30 mg·m^-3 are suggested to be classified as the minimum isolation zone for ammonia leakage.The results show that the accident risk is high and unacceptable when the protection measures are insufficient;the risk of accident related to ammonia can be reduced to a tolerable level when the protective measures given by this research are adopted.If the protection measures are effective,the minimum isolation areas can be limited within the scope of the ammonia-related enterprise.In view of the open-air liquid ammonia reservoirs and the ammonia freezing tunnels,a special liquid ammonia workshop or isolation facility is suggested to construct,which shall be equipped with ammonia alarm device,exhaust hood and water spray,to control the ammonia leakage hazard in the special liquid ammonia workshop or isolation facility.