[JBW1949]

Phosgene gas is a blister agent...If inhaled, it creates blisters in the throat and lungs and you basically drown in your own fluids...

Diphosgene is a liquid...Same thing happens but on your skin...You blister so badly, you dehydrate and die...

[RC one]

Phosgene is classified as a choking agent-it's Chlorine combined with carbon monoxide. It destroys your lungs and mucous membranes. It was an early WW1 era improvement on straight up Chlorine gas such as that used in the second battle of Ypres which is worth reading about

Mustard gasses are the blister agents.

Then came the acetylcholinesterase inhibitors-the nerve gasses.