Plastic Sheeting to Protect Raised Technical Floor

Hello, The installation contractors state that on previous LEED projects they have placed down plastic sheeting down in order to protect the raised technical floor. Correct me if I am wrong but for me this is not a "requirement" in the SMACNA chapter 3 guidebook. This could be requirement if the HVAC system was in the flooring, but this is not the case). 1) Can someone confirm whether of not this is a requirement? 2) Before sealing the floor & installing the carpet does the SMACNA require that cleaning be done underneath the raised floor or is this just a good-practice? Regards, Ian