Air from the H14 HEPA/ULPA filter passes down over the enclosed space, then through two pre-filters and back to the H14 HEPA/ULPA filter plenum chamber. A small absolute filter mounted downstream of the fans generates a loss in the air recycling system, causing an inflow of air between the vinyl curtain and floor.

The vertical air stream carries away powder generated and spilt in the manufacturing process, and passing through the pre-filters is recycled or exhausted via H14 HEPA/ULPA filters. This airflow pattern encourages a floor level air movement to prevent powder drifting through the room, and contamination of sterile products, which are generally kept at least 50 cm from the floor.