·
FDA
recommends maintain minimum 20 air changes per hour in clean rooms.
Horizontal flow : 0.45 m/sec (MPS)
Vertical Flow : 0.3 m/sec (MPS)
Bio Safety Cabinet (BSC): Average of air velocity : 100 feet/minute (FPM) ± 20 %
Horizontal flow : 0.5 m/sec (MPS)
Bio Safety Cabinet (BSC): Average of air velocity : 100 feet/minute (FPM) ± 20 %
Horizontal flow : 0.5 m/sec (MPS)
90 FPM = 0.45 MPS
1M = 3.2808 ft
0.45 X 3.2808 = 1.47636 FPS X 60 = 88.59 FPM
How To Calculate Air
Velocity:
First of all determine the velocity of the air below the HEPA (High Efficiency Particulate Air )filter in
feet per minute.
Check air velocity at the four corners & center of HEPA filter using anemometer.
Calculate the average air velocity of the filter.
It is determined at the four corners and the
center of the filter and the mean of the five readings are determined.
V= (V1 +V2+V3 +V4 +V5) / 5
V= velocity observed at each point,
Calculate the Area of the Filter:
A = l X W
l = length of filter
W = width of the Hepa filter
Calculate the Total air
volume:
T = A X V
V = Average of air velocity in feet per minute
Calculate the Total air in
the room:
V =Volume = L X W X H
Calculate the Air changes per hour:
Air changes per hour = T X 60
/Volume
Ex : T X 60/V
= 80 X 60/800
= 4800 CFH (cubic Feet for hour) / 800
=6
Air changes per hour
Grade- A at least 100 air changes
Grade- C at least 50 air changes
Grade-D at least 20 air changes
Air changes:
Calculate the number of air changes per hour in the area using formula
= average air velocity (ft/min) X Area of the filter (sq ft) X 60 /
Volume of the room (Cu.ft or ft3)
= 90 X 150 X60 / 2400
