How many air changes per hour should my cleanroom have?
February 2, 2012 by Renzo Airflow is usually specified either as average air velocity within the room or as air changes per hour. HEPA & ULPA filters used in most stringent cleanrooms are generally built in ceiling and can be installed in groups housed in a proprietary modular pressure plenum system. They can also be installed in single filter housings, individually ducted, suspended in an inverted “T” grid support system, and sealed to prevent unfiltered bypass air from entering the cleanroom. Cleanroom design conventionally follows the following guidelines for filter coverage:
|
ISO Class |
Fed 208 |
Controls |
Air Velocity at table level in FPM |
Air Changes Rate per Hour |
|
1 |
– | Stringent | 70 – 130 | >750 |
|
2 |
– | Stringent | 70 – 130 | >750 |
|
3 |
1 | Stringent | 70 – 130 | >750 |
|
4 |
10 | Stringent | 70 – 110 | 500 – 600 |
|
5 |
100 | Stringent | 70 – 90 | 150 – 400 |
|
6 |
1,000 | Intermediate | 25 – 40 | 60 – 100 |
|
7 |
10,000 | Intermediate | 10 – 15 | 25 – 40 |
|
8 |
100,000 | Less Stringent | 3 – 5 | 10 – 15 |