the 90 yr old electrical inspector wouldn’t know what a bit of Cat 5e Plenum even looks like... [They] "say" that they are installing pleneum rated cable...nobody checks
It is a problem to check. Riser looks just like plenum, you have to read the printing on the jacket. If there are lots of runs you would have to look at each one to be sure the installer didn't sneak riser in there also.
I'm thinking that it would be a good idea to require cable manufacturers to put a red stripe on all plenum listed cable. That way it could be identified at a glance.
-Hal
