A high containment alternative to isolators

Using downflow booth technology combined with the processing knowledge and experience of Hosokawa Containment engineers, a downflow booth has been designed that has certified operator exposure levels during testing of below 5 microgrammes/m?. This offers less restricted working practices than an isolator the alternative high containment option, as well as positive cost advantages over multiple cell isolator processing for multi-task operations. The system is not designed to replace isolator system technology but rather to give an alternative for some handling operations for the client.

The advantage of such a downflow booth is that the operator can work unrestricted on several processing steps. There is no need for personal protection equipment or for the operator to be suited up, allowing access to all input, processing and output stages within a more user-friendly working environment than through a series of isolator glove ports.

Based on the downward flow of conditioned air passing vertically from the ceiling inlet plenum of the booth, pushing any dust downwards and away from the operator’s breathing zone, the downflow booth offers working flexibility.

Hosokawa Containment, a division of Hosokawa Micron, recently designed and supplied a pair of such downflow booths for a multi-national pharmaceutical company. High containment of product transfer into and out of a small scale tray dryer was specified by the customer in the initial brief with a demand for unrestricted operator access. Independent testing of the downflow booth confirmed that during product transfer from keg to drying trays and from trays to kegs, via a hopper, personal respiratory exposure was maintained below 5 microgrammes/m? over a time-weighted average – even in the event of some spillage of powder, common in this kind of dry powder transfer.

Process Description

Solvent moist raw material enters the booth in lined fibre kegs. The keg is emptied using a hand scoop and the material loaded onto dryer trays. A custom-designed mobile drum raise-and-invert unit was used to facilitate ergonomic keg handling from pallet to working-zone. The loaded trays are then moved along the workbench to be placed into the dryer. The adjustable height workbench can be raised and lowered to facilitate easy tray transfer into the eleven different tray levels within the dryer. Access to the dryer is through hand-ports positioned at different heights, built into a flexible PVC screen curtain that offers additional barrier protection.

When all 22 trays are loaded into the steam heated dryer the drying cycle is started. Due to the restricted access in the customer’s chosen building location for this installation the booths were specifically designed to fit the space available. All filters are accessible from within the booth itself to enable easy filter changes, including that of both the supply and exhaust fine-dust and HEPA filters.

After drying and cooling the trays are manually removed from the dryer with the advantage of the multi-height workbench. Once the product is dry, the potential for airborne particle contamination has increased. The dry powder is manually emptied from the trays into the keg hopper. Operators are protected from the airborne dust by the single-pass downflow of clean air, and additionally a partial upper clear-perspex isolation screen designed such that the operator’s ergonomics are not compromised. The kegs are weighed on an inbuilt balance before being lidded, and then leaving the downflow booth.

Manufacturers looking to safeguard personnel, can be reassured that the performance of the booth has verified by independent testing.

An alternative to restrictive isolator technology for personnel, under certain circumstances, the new downflow developments from Hosokawa Containment offer a cost effective, safe working environment for product transfer.