Table 13.11.

Values of β

Area corresponding with one filter on the ceiling (larger value could be used if air supply outlet is not in the middle /m2)		In unidirectional flow cleanroom, air is supplied with air supply outlets fully on the ceiling and air is returned at two lower bottom sides	0.97
≥15	0.3	In unidirectional flow cleanroom, filters are placed fully (the ratio of blowing area ≥ 80 %)	0.99
>10	0.4	Side supply and side return mode	0.5–0.7 (small value can be used when the distance between air supply outlets is more than 3 m)
>5	0.5–0.7
>2	0.7–0.8	Orifice plate: when placed in the middle with area ≤ 1/2 of the ceiling area;	0.4
>1	0.8–0.9	when placed at both sides with area ≤ 2/3 of the ceiling area
In unidirectional flow cleanroom, filters are placed in between (the ratio of blowing area ranges from 40 to 80 %)	0.9–0.99	Placed fully at the ceiling	0.9–0.95