Clean Room Filter Selection 1

[friartuck]

Hi Everyone

Having done a few clean rooms...like many, I rely on the filter manufactureres to guide me as to the level of filtration required to achieve a particular 'class' of clean room.

For instance, a class 10,000 clean room might need 30AC/hr at a filter level of 99.99% (I made that up so don't correct me if I'm wrong..this is just a hyperthetical value)

My question is, I don't want to rely on the advice of the manufacturer (not that I don't trust them, ...but I should be telling them what filters to use)

Is there a table or guide that indicates the required filtration level and airflow rate for particular classes of clean room.

I have tables of what the filters can do, but not what they can achieve in a room as a whole.

Thanks in anticipation

Friar Tuck of Sherwood

 

[imok2]

This may be of some help:

http://www.lascoservices.com/Federal_Standard_209.pdf

 

[quark]

By filtration level, do you mean filtration area? There are some guidelines for no. of ACPH and filtration area but they are too generous for a pharmaceutical facility. 30 is a good figure and I generally do it at 40.

As a thumb rule, once you fix the no. of ACPH, maintaining a face velocity of not more than 200fpm will ensure 10000 classification for almost all types of pharmaceutical facilities. FFS areas require a bit high filtration area of about 25 to 30% due to high particle generation. There is one good article in ASHRAE Journal about air filtration in pharma facilities and I can tell you the issue no. tomorrow.

You are correct with the filter selection. Regulatory Authorities take it for granted that you should use EU-13 filter terminally for class 10000 areas(core). For change rooms and vestibules, it can be EU-12.

Regards,

 

[Drazen]

In pharmaceutical plants I was working with very clear specifications: they even defined "white" clean rooms and "grey" clean rooms, depending on room function, and had very clear demand about minimal acceptable level of filtration (it allways turns to how many 9's come after decimal point!). Design consultants made that spec's based on USFDA validation demands.

In medical facilities, in several countries, it is allways the same: there is medical norm that mandates what is considered clean.

In both cases I have mandatory demands, and had to choose filters with adequate certificates. As I understand, your position is opposite, am I right? You have to choose filtration level and declare it as "clear room level".

You should be very careful with that because clean room has very concrete meaning in both industries. Regarding food industry I am not sure, I don't know does FDA mandates something, here in Europe food industries I contacted had its own internal definitions of "clean rooms". Once one food company asked me to help them define it and we agreed that their "clean room" should be adequate to "grey room" in pharmaceutical industries ( 2 9's as I remember, but demands are growing virtually every day!)

 

[quark]

Sep'2004 and Aug'2001 issues deal with the subject I referred above.

 

[friartuck]

In Europe we use the designation H11, H12, H13, H14 for the various grades of Hepa filter (to 99.999% efficiency at 0.3 microns (I think for the H14 filter media))and above this rating I believe it goes to ULPA Ultra low penetration, which are designated differently (I think U15,U16 etc)

How does the USA designate their filters??

PS Thanks for the help so far, it is a really interesting subject (with lots of nice little pitfalls and 'grey areas')



Friar Tuck of Sherwood

 

[quark]

http://ssd-rd.web.cern.ch/ssd-rd/DSF/Xreference.htm

This link gives a comparision of Eurovent classification and BS classification.

ASHRAE 52 deals with MERV(Minimum Efficiency Reporting Value) rating of filters. We Indians are still with EU classification.

ULPA filters are tested at 0.1micron particles and you may require it for class 10 and class 1. As far as my experience is concerned, you can do well with EU13(99.997 at MPPS) for class 100 areas.

Go to

http://www.PDHcenter.com

and download the free PDH Course M143 which speaks about design of cleanroom applications. The guidance values of no. of ACPH and minimum filtration area are good.

PS: FDA mandates nothing about filters in particular.

Regards,

 

[MedicineEng]

Here is a star for this post.
Very interesting issue and quite pertaining questions. In fact, what I have noticed in my experience with cleanrooms is that tipically there is a huge safety margin in the design. That is why usually you end with oversized AHUs to cope with overtight specifications of filters (and also over the budget). That is why we have some cleanrooms class 100000 with ULPA filters!!!

I believe that quark is correct when he says that FDA doesn't refer any relation between filter class and cleanliness. This is up to you. If you can achieve your requirements with a lower filter class, fine.

Nevertheless, I would also be very interested to know if there is any guideline or rule of the thumb regarding this subject.

 

[quark]

You should know the internal particle generation and outside particle data if you want to exactly calculate the type of filter and area of filtration.

In the past, we managed with 3 micron filtration for OSD facilities and as the requirements(by the authorities)grew stricter we went for EU-8(>95% at 0.5micron), so that we can have some onsite checking of the filters. The present trend is to go with EU-12(99.97% at 0.3).

I never dared to check actual particle generation when the AHUs are stopped to get the required data, for the particle counters are very sensitive, economically.

With the advent of variable speed technology, the redundancy is restricted to capital budgets and their operation can be as economical as with a conservative design.

The link below gives you some good articles about cleanroom design and filtration system.

http://www.cleanroomsys.com

Regards,