What's the latest news on the ISO Standards and their implementation? On November 29, 2001, the U.S. General Services Administration (GSA) officially announced that Federal Standard 209E, Airborne Particulate Cleanliness Classes in Cleanrooms and Clean Zones, has been canceled and superseded by ISO Standards for cleanrooms and associated controlled environments. The GSA action was the result of a recommendation made by IEST Working Group CC-100 to “sunset” Federal Standard 209E in favor of the ISO documents.
FS 209E is NOT a document controlled by the FDA and thus the FDA was not compelled to issue a change notice (209E and the ISO standards are NOT cGMP guidance documents). The USP had referenced 209E in <1116>.
ISO/TC 209 has developed multi-part documents encompassing the standardization of equipment, facilities, and operational methods. The cornerstone of the standard is 14644 Part 1 and Part 2. The standard is being updated and a new draft will go out for national standards organizations to review and the ISO committee will convene with the aim of agreeing on a revised draft in 3Q12. This revised draft will then go out for public comment. So, as things stand there will be no change to ISO 14644 (parts 1 and 2) until 2013.
ISO 14644 currently consists of the following parts, under the general title Cleanrooms and associated controlled environments:
Part 1: Classification of air cleanliness Part 2: Specifications for testing and monitoring to prove continued compliance with ISO 14644-1 Part 3: Test methods Part 4: Design, construction and start-up Part 5: Operations Part 6: Vocabulary Part 7: Separative devices (clean air hoods, gloveboxes, isolators and minienvironments) Part 8: Classification of airborne molecular contamination Part 9: Classification of surface particle cleanliness Part 10: Classification of surface cleanliness by chemical concentration
ISO 14698 consists of the following parts, under the general title Cleanrooms and associated controlled environments:
Part 1: Biocontamination control – General principles Part 2: Biocontamination control – Evaluation and interpretation of biocontamination data
Cleanliness class designations and quantity have changed from FS209E in 14644-1. Along with the obvious change to metric measure of air volume, ISO 14644-1 adds three additional classes - two cleaner than Class 10 and one dirtier than Class 100,000.
ISO also forces the contractual partners to specify (i) the particle size of interest, and (ii) the state of cleanroom occupancy for certification, i.e., "as-built", "at-rest", or "Operational".
Where can I find any standards or guidelines on Airborne Molecular Contamination? One can start with SEMI F21-1102, which provides a common categorization system as to the acceptable level of acids, bases, dopants and condensables permitted. However the absolute level itself must be set by the owner, user or designer, and more than 9 times out of 10, the database required to knowledgably set the permissible level is proprietary and empirical, built up through long years of experience and testing of materials.
One can also reference the SEMATECH National Technology Roadmap for predictions as to required Wafer Environment Control and Process Critical Materials for future new technology generations. In Particle Measuring Systems (Boulder, CO) Application Note #43, , which discusses their SAW sensor technology for AMC measurement, a molecular contamination level of <0.2 ng/sq.cm./day is considered "clean", and a level of >0.6 ng/sq.cm./day is considered "dirty".
What's the difference between "offgassing" and "outgassing"? Offgassing refers to the release of gaseous materials under atmospheric conditions, outgassing refers to release under sub-atmospheric conditions!
Is it correct to specify a minimum number of "Air Changes per Hour" for a given cleanliness class?
Air changes per hour is a DEPENDENT, and NOT an independent variable. AC/HR is simply the calculation of the air entering the room in one hour (avg. room velocity times the room area - adjusted for units of time if required) divided by the product of the room length, times the room height, times the room width.
While experience may tell us, over time and over hundreds of designs, what AC/HR could be expected to give us the proper required room performance, the AVERAGE ROOM AIR VELOCITY is really the variable of key interest to the designer and the owner.
Full HEPA filtration coverage at the ceiling with low wall or floor air returns creates a unidirectional airflow environment. Less than full HEPA filtration coverage or placement of work surfaces, hardware, support equipment, or people in the air stream creates a non-unidirectional airflow environment. The type of airflow, filtered air velocity, and air changes per hour determine the cleanroom’s ability to meet a classification requirement and how quickly a cleanroom will recover after a contamination event.
Where do I need an airlock? Wherever there is a need to maintain a validatable differential pressures between rooms, AND control of the directionality of flow is critical, then an air lock is normally the solution. At sea level, the Velocity Pressure that can be exerted due to pressure differential is typically equal to 4005 (a constant) multiplied by the square root of the delta P. So, as an example, for a 0.05 inches of water (gauge) differential between rooms, we can expect to see a horizontal velocity component upon door opening of approx. 896 feet per minute!
When should I recommend barrier isolation or mini-environment technology vs. a traditional cleanroom? Process isolation should be evaluated and incorporated wherever it makes sense to do so. Frequently this is NOT a financial decision as much as it is a decision to incorporate "best available technology" and "build quality into the product". Any time you can remove a contamination source from the production process, it is an obvious plus to do so! That's certainly one of the major reasons that all new 300mm fabs are mini-environment-based.
Whenever there is a need to protect the product, such as in aseptic filling, or the personnel and environment - such as in potent drug or live biologicals production - the application of barrier isolation is today the rule, rather than the exception. Because we still need to prove controlled conditions in the event of a breach, and have cGMP functional flows in an FDA validatable facility, most isolator-based life sciences facilities today are being designed to at least an EU Class "C" or "D" - under Operational conditions.
What's cheaper, modular construction or stickbuilt? Every site has to be evaluated on its own merits. "Modular" or pre-engineered cleanroom solutions may often qualify for accelerated depreciation vs. built-in-place construction, and so on an overall evaluated basis, the modular solution is less expensive - but it takes a thoughtful analysis to ensure that the correct decision has been made...modular construction will always be faster than stick-built, and we do not know of any industries today where "time to market" is NOT money!