Step 1: Measure the length, width and height
of the room using a good old fashioned tape measure :-) This will determine the
size of the room or in other words its volume.
Length x Width x Height
=
Step 2: Using a device
called a ‘balometer’ measure the air supply coming out of the HEPA terminal.
You do this by holding the balometer up to the HEPA terminal. The balometer
will catch the downstream of air flowing into the cleanrooms and measures the
cascade speed.
Step 3: Once you have your cascade speed your
next step is to multiply this figure by 3,600 and divide by the room volume.
3,600 = Number of seconds per hour
Remember to round up to
1 decimal point on your final answer!
Example formula:
Cleanrooms
measurements:
Length 9m x Height 7.2m
x 2.8 = 181.44 cm3
Cascade speed is: 0.44
(0.44 x 3,600 ÷ 181.44
= 9 air changes/hr)
You can see from the
above formula this cleanrooms has 9 air changes per hour. Would this be
acceptable for preventing particle contamination?
Answer: No! EU GMP
Annex 1 states the minimum requirement for cleanrooms air change rates is 20
air changes per hour.
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