Yes, with proper handling. In any mechanical refrigeration system, leaks will occur. This fact is exacerbated when the leaks involve odorless refrigerants hazardous to human health, or otherwise harmful for the ENVIRONMENT. 

Having been USED as a refrigerant for more than 150 years, ammonia has a long safety record. The inherent safety of ammonia comes from its characteristic odour, which signals even the smallest leak, at concentrations far lower than any dangerous level. Moreover, its density and very limited range of flammability, advances in safety mechanisms and system designs (plate heat exchangers, separate sealed compartments, leak detection systems, electrical switching outside the compartments ETC.), well-trained individuals working with R717 systems, as well as INDUSTRY codes and standards have made sure that ammonia poses hardly any risk to human health. 

As an example, the United States Chemical Safety Board (CSB) reports that R717 INCIDENTS led to only four fatalities in the ten-year period from 1994 to 2004. This compares with over 800 deaths from lightning strikes in the USA during the same period.

Yes, with proper handling. In any mechanical refrigeration system, leaks will occur. This fact is exacerbated when the leaks involve odorless refrigerants hazardous to human health, or otherwise harmful for the environment. 

Having been used as a refrigerant for more than 150 years, ammonia has a long safety record. The inherent safety of ammonia comes from its characteristic odour, which signals even the smallest leak, at concentrations far lower than any dangerous level. Moreover, its density and very limited range of flammability, advances in safety mechanisms and system designs (plate heat exchangers, separate sealed compartments, leak detection systems, electrical switching outside the compartments etc.), well-trained individuals working with R717 systems, as well as industry codes and standards have made sure that ammonia poses hardly any risk to human health. 

As an example, the United States Chemical Safety Board (CSB) reports that R717 incidents led to only four fatalities in the ten-year period from 1994 to 2004. This compares with over 800 deaths from lightning strikes in the USA during the same period.