If there is a significant generation of particles in the process, the higher number in the range is selected. Mecart uses a proprietary cleanroom airflow calculator, and we assumed 10 to 30 ACH for an ISO 8 30 to 65 ACH for an ISO 7 80 to 150 ACH for an ISO 6 200 to 450 ACH for an ISO 5. Various recommendations for air change ranges can be found on the Internet. Notice that the term “range” is used and not “value”.Ī cleanroom with activities that generate few particles versus one that generates a lot of airborne particles, even if both are ISO 7, will not require the same air changes per hour. However, the ISO cleanliness level (ISO 8, 7, 6, and 5) gives a hint on the ACH range required. ISO classification doesn’t dictate airflow The concentration of particles of ≥0.5 µm should be below 352,000 particles of ≥1 micron should be below 83,200 and particles of ≥5 microns should be below 2,930. The ACH is the number of total replacements of a room's air in one hour, and the ISO 14644-1:2015 only tells you the result that you must aim for: the maximum concentration limits for particles.įor example, for an ISO Class 7 cleanroom, particles smaller than 0.5 microns (≥0.1 µm, ≥0.2 µm, ≥0.3 µm) are not taken into consideration. The standard ISO 14644-1:2015 does not specify the air changes per hour (ACH) for each cleanroom class because it depends on many factors. However, classification alone isn’t sufficient for calculating the airflow.
This means that the HVAC system must be capable of conditioning more than double the air. The amount of air is different in an ISO Class 6 and ISO Class 8 cleanroom. It takes a mix of engineering skills, understanding the particle-generating potential of the process, and experience. Cleanroom HVAC engineering is not an easy thing.
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