Newer electronic equipment rooms, such as high-heat-density data centers and communication areas, may utilize cooling equipment equipped with newer technologies, such as in-row or in-rack cooling units. Sometimes, these units even include containment systems. However, there are lots of cooling systems still in use that rely upon computer room air-handling units (AHUs) with supply air directed down into a raised floor plenum. Often, these types of systems are not well understood by site personnel or the engineers who design them. This article will shed some light on the basics needed to understand raised floor plenums and expand upon their shortcomings.
During my time providing engineering for military communication sites, I often visited dozens of sites around the world and had firsthand experience with raised floor plenums. Site details in this paper are intentionally vague to preserve security needs.