Combined with Exhausts
Mostly the use of a supply inlet as a local ventilation system presumes that the supply device (with air from outside the room) is located inside a large room, which also has an adequate exhaust airflow rate or has convenient exhaust/transfer openings for the airflow. It is also necessary that the exhaust flow rate is maintained (or pressure difference kept). Otherwise the air supply could change in rate or direction. Instead of using air from a ventilation system, the supply air could be taken from the room (volume) it is situated in. In this case, the room must also have a supply and an exhaust flow rate. It is often necessary to clean the air before it is used in the supply inlet.
A supply inlet could be designed with or without an exhaust. There should naturally be an exhaust opening in the room. If the influence of the exhaust on the supply inlet is low, then it requires no special design, but if the influence of the exhaust is large it must be taken into account. The inlets could be combined with specific exhaust hoods to enhance their efficiency (see Section 10.4). There are many ways to design supply inlets and also to combine different supply inlets; just a few inlets are described in this section.
All supply inlets without a specific exhaust have the same problem, the spreading of contaminants in the room outside the supply air zone. When the inlets are used to create a cleaner zone in a normal workroom this is usually no problem. When a supply inlet is used to blow away some hazardous contaminant it is necessary to combine it with a specific exhaust, or the rest of the room will be contaminated.
Posted in INDUSTRIAL VENTILATION DESIGN GUIDEBOOK