Cleanrooms are not all the same, various levels of air purity exist. This is what we mean by an ISO class. The International Standards Organization has divided cleanrooms into nine distinct levels of classification based on the amount of particles allowed per cubic meter. The lower your classification the less particles are permitted in the cleanroom.
ISO1
- Up to 10 particles ≥ 0.1 micrometers
ISO2
- Up to 100 particles ≥ 0.1 micrometers
- Up to 24 particles ≥ 0.2 micrometers
- Up to 10 particles ≥ 0.3 micrometers
- Up to 4 particles ≥ 0.5 micrometers
ISO3
- Up to 1,000 particles ≥ 0.1 micrometers
- Up to 237 particles ≥ 0.2 micrometers
- Up to 102 particles ≥ 0.3 micrometers
- Up to 35 particles ≥ 0.5 micrometers
- Up to 8 particles ≥ 1 micrometer
ISO4
- Up to 10,000 particles ≥ 0.1 micrometers
- Up to 2,370 particles ≥ 0.2 micrometers
- Up to 1,020 particles ≥ 0.3 micrometers
- Up to 352 particles ≥ 0.5 micrometers
- Up to 83 particles ≥ 1 micrometers
ISO5
- Up to 100,000 particles ≥ 0.1 micrometers
- Up to 23,700 particles ≥ 0.2 micrometers
- Up to 10,200 particles ≥ 0.3 micrometers
- Up to 3,520 particles ≥ 0.5 micrometers
- Up to 832 particles ≥ 1 micrometer
- Up to 29 particles ≥ 5 micrometers
ISO6
- Up to 1,000,000 particles ≥ 0.1 micrometers
- Up to 237,000 particles ≥ 0.2 micrometers
- Up to 102,000 particles ≥ 0.3 micrometers
- Up to 35,200 particles ≥ 0.5 micrometers
- Up to 8,320 particles ≥ 1 micrometer
- Up to 293 particles ≥ 5 micrometers
ISO7
- Up to 352,000 particles ≥ 0.5 micrometers
- Up to 83,200 particles ≥ 1 micrometer
- Up to 2,930 particles ≥ 5 micrometers
ISO8
- Up to 3,520,000 particles ≥ 0.5 micrometers
- Up to 832,000 particles ≥ 1 micrometer
- Up to 29,300 particles ≥ 5 micrometers
ISO9
- Up to 35,200,000 particles ≥ 0.5 micrometers
- Up to 8,320,000 particles ≥ 1 micrometers
- Up to 293,000 particles ≥ 5 micrometers
Particle Size Matters
As seen above the size of particles matter. Significantly more 0.5 micrometer particles are allowed than 5 micrometer ones. As such it’s important to know the size of particles when determining the standard of cleanroom that you need constructed.
If you wanted a cleanroom with a maximum of 100 particles per square meter you would need a lower classification for particle of 0.5 micrometers compared to 5 micrometer particles.
What ISO Classes Mean for You
More than anything your purpose is what determines the ISO class you choose. Different industries have different classes they default to. Ultimately it all depends on permissible particle count, particle size and required air circulation.
When an ISO class is settled on, there is more to keep in mind though. For example, cleanrooms of ISO level 7 or lower should include a changing atrium. This helps prevent contamination being brought into the cleanroom by personnel entering.
ISO class is also going to affect testing your cleanroom. Due to the lower maximum particle counts ISO class 5 and lower need to be tested every six months, while 6 and higher need to be tested yearly.
Similarly, your ISO class will determine cleaning processes. Knowing how to properly maintain your cleanroom is vital to ensure compliance to ISO guidelines. As you might expect ISO class 1 cleanrooms require a very thorough process to maintain compliance when compared to higher levels.
