Which gas is classified under group A1?

Trifluoromethane, also known as HFC-23, is classified under group A1 in the context of refrigerants and certain gas classifications. Group A1 refers to substances that are non-toxic and have low flammability. Trifluoromethane is a fluorinated hydrocarbon that meets these criteria, making it safe for use in various applications, including refrigeration and air conditioning systems.

In contrast, the other options provided do not fit the A1 classification. Butane, while non-toxic, has a higher flammability risk, and ammonia is classified as toxic. Methane, although it is non-toxic, is considered flammable, which also disqualifies it from group A1. Understanding these classifications is essential for compliance with safety regulations and ensuring the proper handling and use of different gases in mechanical applications.