Hot and cold aisle containment explained

Servers take in cool air at the front and blow hot air out of the back. If those air streams mix, cooling units work harder and some equipment still runs hot. Containment keeps them apart.

Hot and cold aisles

Racks are arranged in rows facing each other: fronts face fronts (the cold aisle) and backs face backs (the hot aisle). Cooling supplies air to the cold aisles and draws it back from the hot aisles.

Adding containment

• **Cold aisle containment** encloses the cold aisle with doors and a roof, so supply air goes only into equipment intakes.
• **Hot aisle containment** encloses the hot aisle and returns exhaust air directly to the cooling units.

Either approach reduces mixing; the right choice depends on the room layout and cooling system.

The small things matter

Blanking panels in unused rack spaces, brush strips where cables pass through, and sealed gaps under racks make as much difference as the containment itself.

Measure the result

Place temperature sensors at the top, middle and bottom of rack fronts. Even intake temperatures show that containment is working.

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