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cleanroom classification, cleanrooms, iso 14644 - cleanrooms and controlled environments, particle counts
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  #9  
Old 5th November 2011, 07:21 AM
SGquality SGquality is offline
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Re: ISO Class 7 Clean Rooms - built as Class 8 but complies with requirements of Clas

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In Reply to Parent Post by somashekar View Post

Not knowing your product that you handle in the clean room, it is not too easy to suggest. However the selction of the clean room class and the processes performed thereafter as against requirement is a matter of risk assessment and supported by valid product testing.
Calling out your clean room as Class 7 and yourself is far less important than claiming meeting or exceeding class 8 and supporting the same with periodic validation and product test reports meeting to requirements.
Thanks Somashekhar.

I would like all experts to comment on the engineering aspects of the Clean Room and not considering the product.

Conceptually, would a clean room be designated entirely based on particle counts ? If it was a Class 5 clean room, there are lots of things required like gowning / degowning area, wearing sterile garments etc. Like these, would there be any additional requirements between Class 7 and 8 ?

Sorry for taking this long

Last edited by somashekar; 5th November 2011 at 08:02 AM.

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  #10  
Old 5th November 2011, 08:12 AM
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Re: ISO Class 7 Clean Rooms - built as Class 8 but complies with requirements of Clas

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In Reply to Parent Post by SGquality View Post

Thanks Somashekhar.

I would like all experts to comment on the engineering aspects of the Clean Room and not considering the product.

Conceptually, would a clean room be designated entirely based on particle counts ? If it was a Class 5 clean room, there are lots of things required like gowning / degowning area, wearing sterile garments etc. Like these, would there be any additional requirements between Class 7 and 8 ?

Sorry for taking this long
Yes.
A class 7 clean room is 10 fold better than class 8 as you can see from the ISO14644-1.
So the gowning, materials selection and cleanroom behaviour must be more better to always maintain a class 7 as compared to class 8.
Some details below for particle details.

Where do particles come from?
Clean Room Air
The task of the Clean Room filter is to ventilate the atmosphere with microbial and particulate free air. They create a positive pressure, so that any air-borne contaminants present are from within the room.
The source of micro-organisms is from people.
The source of particulates are from people and processes.

Microbes
Microbes are dispersed from skin cells, and a human body sheds the outermost layer of skin every 24 hours.

1 BILLION SKIN FLAKES EVERY 24 HOURS.

A skin flake is typically 33 microns - 44 microns. They break down to typically 20µ (micron) but 7-10% are less than 10µ (micron). The equivalent diameter of bacteria carrying particles is 12-14µ (micron). These settle by gravity at 0.37 meters per second.

12-14µ (micron) size particles will settle in wounds of hospital patients and aseptically filled containers in pharmaceutical applications by gravity.

Inert Particles

Particles from people are dispersed:

From their skin

From their normal outdoor clothing

From their Clean Room clothing (both through it and from the surface).

The mixture of skin flakes and fabric fibers fragment into smaller pieces, so that the total number of particles is:

10 BILLION EVERY 24 HOURS. This figure is dependent on activity rate, work activity, more particles.

Demonstrations have indicated that typically this means:

1 MILLION PARTICLES EQUAL TO OR GREATER THAN 0.5 MICRONS ARE DISPERSED EVERY MINUTE.
They disperse into the air from exposed skin, through the apparel fabric and also out through the neck, waist, trouser opening and wrists.

(Courtesy http://www.mvent.com.ph/references/cleanroom.htm)

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  #11  
Old 5th November 2011, 06:27 PM
Ronen E Ronen E is offline
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Re: ISO Class 7 Clean Rooms - built as Class 8 but complies with requirements of Clas

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In Reply to Parent Post by somashekar View Post

The equivalent diameter of bacteria carrying particles is 12-14µ (micron). These settle by gravity at 0.37 meters per second.
37 cm per second? Sounds like an error to me. If anything, that would be correct at completely still air, which is hardly ever the case in an active clean-room environment. Particles movement patterns and rates depend on many factors, for instance clean-room design, flow settings, type and level of activity inside, personnel movement (type, level, speed) etc.
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Old 3rd December 2011, 05:33 AM
Nigel D Lenegan Nigel D Lenegan is offline
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Re: ISO Class 7 Clean Rooms - built as Class 8 but complies with requirements of Clas

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In Reply to Parent Post by harry View Post

Amazing! Unless somebody replaced the filters. Otherwise, my first suspicion will be on how the particles counts were measured. Did you get an independent lab to verify it?
Hi,
In my experience of validation of pharmaceutical cleanrooms, they are often orders of magnitude cleaner than required. Rather than asking can we re-classify as ISO 7, why not consider reducing airchange rates, significantly reduce HVAC running costs and probably still achieve better than ISO 8???
Cheers
Nigel
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  #13  
Old 3rd December 2011, 11:52 AM
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Re: ISO Class 7 Clean Rooms - built as Class 8 but complies with requirements of Clas

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In Reply to Parent Post by Nigel D Lenegan View Post

Hi,
In my experience of validation of pharmaceutical cleanrooms, they are often orders of magnitude cleaner than required. Rather than asking can we re-classify as ISO 7, why not consider reducing airchange rates, significantly reduce HVAC running costs and probably still achieve better than ISO 8???
Cheers
Nigel
Hello Nigel! Welcome to the Cove! In looking at your profile, you have a true expertise that will be handy in many of our threads. I hope you stick around and pitch in as much as you can!

But to your point, I was considering typing something until I saw your post, which is exactly what I was thinking. It should be need-based. Clearly identify your need, and then assure it meets that requirement. In my experience, it's always easier to explain going from loose to tighter requirements. It's much more involved explaining going from tight to looser tolerances.

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Old 15th December 2011, 04:57 AM
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Re: ISO Class 7 Clean Rooms - built as Class 8 but complies with requirements of Clas

Thanks all who responded to my question.

I found reference in ISO 14644 -4 saying that the number of air changes in ISO Class 8 is 10-30 while in ISO Class 7, it should be between 30 - 70.
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Old 15th December 2011, 08:02 AM
Nigel D Lenegan Nigel D Lenegan is offline
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Re: ISO Class 7 Clean Rooms - built as Class 8 but complies with requirements of Clas

Hi,
You are referring to Table B.2 "Examples for Microelectronics Cleanrooms", from my contacts in the industry who wrote this were probably concerned about heat gain mitigation than cleanliness. I am involved in writing a british standard for cleanroom energy managment which will advocate a more considered approach. to all sector cleanroom designs.

The reasons for me joining blogs like this is to try and influence the sector to see things a little different, and not be tied to 50-60 year old, folklore on required airchange etc which has no solid basis other than it worked in the space race in the 50's for gyroscope manufacture....

From a Pharmaceutical perspective and my experience of cleanroom design and operations / validation, I can guarantee in many cases, that so long as the gowning strategy, operator competance and internal equipment gains and microbial particulate are under control and the room ventilation system is HEPA filtered, and effective at dilution, much lower airchanges are possible.

Hence using a risk based / scientific approach airchanges can be justified as low as ISO 5 = 15-20, ISO 6 = 10-15 and ISO 8 <10. Considering the fan power v flow laws significant savings are possible especially within over-designed and over-performing existing facilities (the root of this thread). Plus new facilities can be much smaller, less costly and cheaper to run.

I accept FDA suggests min 20 ac/hr and WHO advocates 6-10, but to reiterate given a robust risk based assessment, lower is achievable and in many cases better to avoid lower level re-entrainment of particulate.

Anyway - I welcome a reasoned discussion / argument.

Thanks Nigel
Thanks to Nigel D Lenegan for your informative Post and/or Attachment!
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Old 15th December 2011, 08:35 AM
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Ajit Basrur Ajit Basrur is offline
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Re: ISO Class 7 Clean Rooms - built as Class 8 but complies with requirements of Clas

Thanks Nigel. Your approach sounds very logical and with smaller air changes as well, the Particulate Counts could meet the acceptance criteria.

But to answer the OP question, what is your opinion on reclassification of clean room from ISO Class 8 to ISO Class 7 ? Would there be any additional requirements ?

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