ISO 14644-1 Clean Room Occupancy State Validation Requirements



According to revised version of ISO 14644-1, there is a revised statement which is as follows:

Occupancy state(s)
The air cleanliness class by particle concentration of air in a cleanroom or clean zone shall be defined in one or more of three occupancy states, viz. “as-built,” “at-rest” or “operational”

Does this mean, even the newly built clean room does not need to be validated in three state? only validating in one occupancy state is enough? Any kind of help will be appreciated. Thanks.


Looking for Reality
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Howdy Nyeli,

Do not confuse "defined" with "Validated". And certainly do not confuse either of this with "Acceptable" or "Fit for Use".

I set out to build a clean room...I must first define the level of cleanliness to achieve. Let us say Class 1000 (~ISO6)...that is not a complete definition of the goal...I also need to know how the room is used, and whether the room is currently in use during the measurement...or ever has been.

In most clean rooms, the dirtiest thing is the people in it.
If there are no people in it, it is easier to have a cleaner room.

Class 1000 'as built' means that it has never been used and had human traffic doing the intended is just as brand new. This is the cleanest the room will likely ever be.

It is a good measure for paying the guy who built the is the best that the room is likely capable of.

Class 1000 'at rest' means that people have done normal daily use in the room and done the intended work that the room was built for...but they are not doing it now during my test. There has been time for all of the human dirt, and process particulate to be purged from the room. It isn't as clean as brand new...but usually it is cleaner than when people are in it moving around doing their work.
This is often a measurement used to make sure ventilation systems and filters are working is what the room is capable of now that you've been using it.

Class 1000 'in operation' or 'operational' means that you are measuring the air quality during the normal course of the day while the room is occupied with people doing things and moving around...this is usually the dirtiest time since the people provide most of the airborne particulate, and stir up particulate from surfaces.

This is a measurement of what you and the parts you are making actually experience. This is the number most customers care about. Every 'validation' I have ever done for a customer has been mandated to be in 'operational' state.

For verifying that a room is 'clean enough' or 'meets the standards for the process'...most everyone I know will go only by the "operational" test data.
The parts that you need to keep clean are typically exposed to the air during operations, not when 'at rest'.



Thank you so much Ninja for your time. I'm still wondering where in the guidelines or requirements say it clearly that we need to validate 'in operation' state? Should I say "No" if somebody wants to validate only on "At Rest" state. Thank you.


Looking for Reality
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I don't have a direct answer to your question.

The standard is just that...a standard. There is guidance to know the difference between the three states, and tag your measurement to the state so that the measured number is not misleading...makes sense.

"Requirements" (presupposing that you are maintaining a cleanroom to achieve a purpose)...would come from the purpose. In most cases (in my experience)...that purpose is satisfying a customer whether by meeting a stated requirement or providing an in spec part with acceptable yield (profit).

What purpose are you trying to achieve?
What you should do next (the plan) will derive from that.
If your purpose is just to follow the standard, it looks like you're already done.
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