This study essentially concerns refrigeration installations using ammonia as a refrigerant. However, in order to better understand and to place the risks associated with these installations in perspective, quantified information has also been collected on numerous accidents, both French or foreign, in other industrial or agricultural activities and in the field of transport. The processing of these data allows a number of comparisons to be made using general indicators (geographic distribution, nature, accident causes and consequences, etc.). Furthermore, while the nature and significance of the hazards presented are particularly different, the case studies bring into play liquid, gaseous ammonia or its aqueous solutions. These various phases can be presented for a given activity or during an accident (normal physical state of the product, transfer of risks or pollution during an intervention in a normal or accidental situation, etc.). Excluding special cases that are especially associated with the type and the consequences of certain accidents, the ammoniacal solutions used as liquid fertilizers are not taken into account, however. The sample studied consists of: