2.9. Piston ventilation (PiV)
In this method of air distribution, air is supplied vertically or
horizontally across the whole room at low velocity (typically 0.2e
0.4 m/s) and turbulence to create a “piston” type flow, see Fig. 14.
This is a very effective way of removing contaminants from the
room but it is also costly and requires a very high air change rate
(200e600 air changes per hour). Hence, it is only used in certain
applications, such as clean rooms and hospital operating theatres