Your access floor may be spotless, but that is not what is important.  The space between the concrete subfloor and the raised floor is an air plenum.  If that subfloor is dirty, particulate can easily migrate into the hardware on the raised floor platform.    

Subfloor contamination can have a detrimental effect on disk drives, robotic storage units, circuit boards, logic boards and environmental systems such as Fire Suppression systems, and HVAC units.  All of these are a necessary link to the up- time expectations of Data Centers and HUB Server rooms.