In-line centrifugal fan suitable for both vertical (upwards) and horizontal mounting. The unit casing shall be heavy gauge galvanised steel. The fans shall be of high efficiency backward curved centrifugal design, manufactured in galvanised steel. Fans shall be direct or belt drive with EFF2 high efficiency motors to BS5000 as standard. The unit motor shall be positioned outside the ventilation airflow path. The unit shall be capable of continuous operation at 90°C. The unit shall have speed control or starter as standard.