Info needed: Foam extinguishers fitted on trucks

[motto]

On the lighter side. It's a little off topic but it does relate to fire extinguishers.
For putting out engine fires the DC3/C47 used two CO2 extinguishers installed in the cockpit behind the first officers seat with plumbing out to the engines. I was working on a company aircraft in Lae, PNG that required both bottles to be changed for being time expired. The engineer doing the job thought he would give the crew working on one of the engines a bit of a surprise and pulled the appropriate fire handle. Unfortunately he had forgotten that he had already undone the pipe connection or someone beat him to it. The cockpit instantly filled with a dense white fog as he damn near extinguished himself.
You could say that the joke backfired on him.

David