599383 A greenhouse air distribution system providing uniform airflow is disclosed. The system comprises a plurality of tubes (200) to distribute air. The tubes (200) comprise an inner tube (204) within an outer tube (202). A main air flow is supplied to the interior of at least one of the inner tubes (204) and the air pressure within the inner tube varies along its length. The tube comprises inner tube holes (208) to allow air to pass from the inner tube (204) to the outer tube (202) and outer tube holes (206) to allow air to pass into the greenhouse. The inner (204) and outer (202) tube holes are offset from each other. The inner and outer tube holes are configured to provide for a substantially uniform air distribution into the greenhouse along their lengths.
