The hot aisle / cold aisle arrangement is a concept for efficient cooling in server rooms and data centers. Servers are positioned in rows so that cold aisles (air intake) and hot aisles (exhaust) alternate. This separation prevents hot exhaust air from mixing with cooling air, significantly improving cooling efficiency. Containment enclosures around the cold or hot aisles enhance the effect further. For your ISMS, climate control is part of physical security: overheating can cause system outages and thus availability violations. Document the cooling architecture and monitor temperatures with alarm thresholds.