Principles of Design Recirculating Downflow Containment Booths are an industry recognised standard and utilise a push/pull airflow principle. A unidirectional flow of air is forced downward through ceiling mounted distribution screens ensuring a vertical flow. This suppresses the elevation of dust, taking it away from the operator's breathing zone and into the integral filtration system. Once Through Used in applications where the presence of solvent fumes and vapours are anticipated. In this instance, both exhaust and supply fans will be required, ensuring that the solvent air will not be recirculated back into the operator's beathing zone.