This is one of the main differentiators between cold-aisle and hot-aisle containment. 

Raised floor environments are commonly associated with cold-aisle containment, as conditioned air supplied beneath the floor is delivered through perforated tiles directly into the aisle. 

Slab environments (where no raised floor exists) more often use hot-aisle containment, where hot exhaust air is captured and returned via ceiling plenums or ducting. 

Row-based cooling systems provide additional flexibility, as they can support either configuration without requiring raised floors.