An equipment enclosure comprising: an enclosure housing having a front side, a first side, a second side, a back side, a top side and a bottom side; an equipment frame disposed within the internal area of the enclosure housing, such that a first side area is formed between the first side of the enclosure housing and a first side of the equipment frame, a second side area is is formed between a second side of the equipment frame and the second side of the enclosure housing, a front area is formed between the front side of the enclosure housing and a front side of the equipment frame, and a back area is formed between the back side of the enclosure housing and a back side of the equipment frame; characterized in that the equipment enclosure is configured to simultaneously accommodate equipment components using a front-to-back cooling airflow and equipment components using a side-to-side cooling airflow, and that it further comprises: a first internal panel (32, 34) disposed between the first side of the equipment frame and the first side of the enclosure housing and extending vertically along at least a portion of the height of the equipment frame, to provide a substantially air tight seal between the first side area and the back area and to define the first side area as a substantially enclosed intake air plenum extending from the top side to the bottom side of the enclosure housing; and a second internal panel disposed between the second side of the equipment frame and the second side of the enclosure housing and extending vertically along at least a portion of the height of the equipment frame, to provide a substantially air tight seal between the second side area and the front area and to define the second side area as a substantially enclosed exhaust air plenum extending from the top side and the bottom side of the enclosure housing, the exhaust air plenum being opposite to the intake air plenum. an enclosure housing having a front side, a first side, a second side, a back side, a top side and a bottom side; an equipment frame disposed within the internal area of the enclosure housing, such that a first side area is formed between the first side of the enclosure housing and a first side of the equipment frame, a second side area is is formed between a second side of the equipment frame and the second side of the enclosure housing, a front area is formed between the front side of the enclosure housing and a front side of the equipment frame, and a back area is formed between the back side of the enclosure housing and a back side of the equipment frame; characterized in that the equipment enclosure is configured to simultaneously accommodate equipment components using a front-to-back cooling airflow and equipment components using a side-to-side cooling airflow, and that it further comprises: a first internal panel (32, 34) disposed between the first side of the equipment frame and the first side of the enclosure housing and extending vertically along at least a portion of the height of the equipment frame, to provide a substantially air tight seal between the first side area and the back area and to define the first side area as a substantially enclosed intake air plenum extending from the top side to the bottom side of the enclosure housing; and a second internal panel disposed between the second side of the equipment frame and the second side of the enclosure housing and extending vertically along at least a portion of the height of the equipment frame, to provide a substantially air tight seal between the second side area and the front area and to define the second side area as a substantially enclosed exhaust air plenum extending from the top side and the bottom side of the enclosure housing, the exhaust air plenum being opposite to the intake air plenum. a first internal panel (32, 34) disposed between the first side of the equipment frame and the first side of the enclosure housing and extending vertically along at least a portion of the height of the equipment frame, to provide a substantially air tight seal between the first side area and the back area and to define the first side area as a substantially enclosed intake air plenum extending from the top side to the bottom side of the enclosure housing; and a second internal panel disposed between the second side of the equipment frame and the second side of the enclosure housing and extending vertically along at least a portion of the height of the equipment frame, to provide a substantially air tight seal between the second side area and the front area and to define the second side area as a substantially enclosed exhaust air plenum extending from the top side and the bottom side of the enclosure housing, the exhaust air plenum being opposite to the intake air plenum.