Which hazardous byproduct is produced when common refrigerants decompose in the presence of open flame?

When common refrigerants decompose in the presence of open flame, phosgene gas is produced as a hazardous byproduct. This occurs because many refrigerants contain chlorine and carbon compounds. When exposed to high temperatures, such as those from an open flame, the chemical structure of these refrigerants can break down, resulting in the formation of phosgene.

Phosgene is particularly dangerous because it is a toxic gas that can cause serious respiratory issues and even death at certain concentrations. Its production during the decomposition of refrigerants is a critical safety concern for professionals working with these substances, requiring strict safety protocols to prevent combustion or improper disposal.

The other substances listed may be associated with different chemical reactions or processes, but phosgene is specifically linked to the decomposition of chlorinated refrigerants when exposed to flames, making it the correct answer in this context.