In the early 1960s the fire service was able to make interior attacks on house fires that were often able to be made without the use of self-contained breathing apparatus, (SCBA) Granted, in those days SCBAs weren't readily available or used by many departments and there were many who saw it as a sign of weakness to even bother with them.
Then in the late 60's and early 70's the nature of house fires in general changed dramatically.
With the introduction of polyurethane foam, (often described as compressed gasoline), as a replacement for Jute furniture padding, one of the most feared phenomena for all firefighters swiftly became an almost regular occurrence. Flashover....