Why We Undertake Particulate Testing to ISO Class 7 or 8 for Data Centres

Airborne particulate testing is essential to data centers and/or server rooms; however before you undertake the testing you need to know what ISO rating you need to achieve for the verification process. Most new data centers need to achieve an ISO rating of 7 or 8.

It’s worth noting that Class 7 and Class 8 ISO standards do not specify any limits on particles smaller than 0.5 micron. To be eligible for a Class 1 to Class 6 rating, smaller particles (0.3 um and smaller) must be measured and limited. Unfortunately, in a data centre/server room environment, air filters that block particles smaller than 0.5 micron would dramatically impede air flow, which would place huge strain on the cooling system which is a huge ongoing cost for any data centre and/or server room. Therefore, although achieving a Class 6 (or lower) rating would lead to a ‘cleaner’ room, it would usually lead to a much higher cost to the cooling of cleanroom area than is practical.


To be classified as a minimum Class 7 clean room environment, there can be no more than 352,000 particles of a size 0.5 micron or larger per cubic metre of air (pcm). Class 8 allows 3,520,000 such particles pcm and each class also has limits on the number of 1 and 5 micron particles allowed within the containment.

In any environment, particles above 1 micron in size will eventually fall to the floor and unless the particles are removed by cleaning, will remain in place. Some of the particles may be carried in directed air flows and will be trapped but the majority can only be removed from the environment via detailed cleaning.

Airborne particles smaller than 0.5 micron pass through the filters and are not efficiently removed from the room but instead remain circulating. That is why this particular size is used as a reasonably realistic marker for room preparation, cleanliness and potential cleanliness as these smaller particulates can hang in the air and pass-through air flow filters which is not ideal.

How Do We Measure the Particles in Data Centres?

We measure airborne particles in data centres etc. using our particle counters. We follow the latest ISO 7 & 8 methods which specifies the frequency of sampling locations for any particular space, taking into account the size and shape of the clean room enclosure. In addition, we also take particulate measurements at other known risk areas such entrance doors, fresh air intake and AHU exhaust systems.  Once the particulate testing is complete, we will interpret the results within our comprehensive indoor air quality reports. Our particle counters are UKAS calibrated annually.

On-Site ISO 14644-1 Particle Counting

We measure airborne particles using the protocol outlined in ISO Standard 14644-1 for testing cleanrooms.

This can be as part of a new-build handover report or ongoing periodic testing. We measure for particle density at key areas such as near each air handler, fresh air, fresh air makeup, and at the prescribed number of locations through the room. If the particle count appears high, we will try to determine the cause.

We can help with your Particle Counting Testing to ISO 14644-1:2015

We have large amount of experience in understanding the requirements of Particulate Testing for ISO 14644-1 for cleanrooms, along with extensive experience of carrying out many tests on data centres across London and the Southeast.

Please download our airborne particulate testing checklist for more information on how to prepare your cleanroom for your particulate testing to ISO 14644-1. To find out more about our airborne particulate testing service, or if you wish to discuss your project please contact us on 01525 303905 or email us at info@aptoundtesting.co.uk