Back in the late 60’s, when I went through NBC Warfare School, it was called a blister agent....
When I went through NBC training, it was considered a choking agent. It doesn’t produce the blisters typical of a mustard gas. those are very distinct. Phosgene ultimately impairs respiratory gas exchange. In other words, it chokes you.
https://en.wikipedia.org/wiki/List_of_chemical_warfare_agents