Localized air delivery system as a protection tool

Only the localized control of clean air flows can claim to ensure high levels of air cleanliness around products sensitive to airborne contamination. It is of course possible to achieve good overall particle protection in large volumes such as production workshops, even if they are open to internal contamination (operators, machines, raw materials, etc.). But localized control, also known as "unidirectional flow" or "directed flow", makes it possible to achieve "class 5" levels of cleanliness in local operations (from the ISO 14644-1 ), or "class 100" (from the former FED-STD-209 E standard) in environments that can hardly reach cleanliness classes 100 times lower in clean rooms disturbed by activity ("class 7" from ISO 14644-1 or "class 10,000" of FED-STD-209 E).

This observation is now shared by a large number of food manufacturers, for whom the issue of cold and working conditions is added to that of ultra-cleanliness. Good localized control of clean, cold air flows enables a constantly low temperature of around 4°C to be maintained at the level of the food products being processed (worktops, packaging machines, conveyor belts, etc.), while ensuring a much higher temperature of around 15°C in contact with people located nearby.

This article will begin by defining what is meant by localized protection by clean air blowing, and then describe the physical phenomena involved in environmental separation devices. In particular, the effects of entrainment, mixing and buoyancy will be discussed, as will the dynamics of particle transport. Finally, concrete localized protection technologies will be presented and described.