Construction is just the beginning of the process of getting a cleanroom operational. The next step is certification. Why is it important, how is it done, and who regulates it?

The National Environmental Balancing Bureau (NEBB) is an international certification association whose members test and certify cleanrooms. Founded in 1971, the not-for-profit organization develops standards, procedures, and programs for cleanroom certification and testing, and adjusting and balancing environmental systems. It also develops standards for measuring sound and vibration of building systems, commissioning building systems, retro-commissioning existing building systems, and performance-testing fume hoods. The NEBB offers technical training and development, and operates programs to certify firms and individuals who meet and maintain NEBB standards.

The NEBB’s publication Procedural Standards for Certified Testing of Cleanrooms establishes a “uniform and systematic set of criteria for the performance of cleanroom testing and certification.” The standards and procedures in this manual are intended to be the minimum requirements that an NEBB Certified Cleanroom Performance Testing (CPT) Firm will follow when it tests and certifies a cleanroom.

Recognized certification activities typically include airflow velocity and uniformity tests, HEPA filter installation leak tests, room particle count tests, enclosure pressurization tests, temperature and humidity uniformity tests, sound and vibration tests, light level and uniformity tests, recovery tests, conductivity tests, particle fallout count tests, and electrostatic tests.

What is certification?

“To our customers, certification can mean different things. We get calls weekly requesting to certify this thing or that,” says Stefan Hocom, manager, cleanroom certification, CPS Certification Services Inc., Aptos, Calif. “Most are referring to an ISO classification test; some are referring to an overall evaluation that involves expansive testing as well as evaluating personnel, written protocols, etc. Others have one specific area of concern, [such as] ‘I want my HEPA filters certified’ or ‘I have a product I want to have cleanroom-certified.’ My mentor in this industry used to provide an all-encompassing cleanroom certification that included an evaluation of absolutely everything. It ranged from an inspection of the cleanroom seals and interstitial spaces to the type of mop and bucket used by the janitorial staff and everything in between.”

Hocom adds that the most accurate definition of “cleanroom certification” would be the ISO 14644-1 classification test, which involves definitive pass/fail criteria. ISO 14644-1 is part of a series of documents, being developed as International Standards, concerned with cleanrooms and associated controlled environments. The standard considers the classification of air cleanliness for these spaces solely in terms of the concentration of airborne particles. Only particle populations having cumulative distributions based on the lower threshold particle sizes ranging from 0.1 to 5 µm are considered.

“Essentially the process is a combination of testing, observation, and calculation,” Hocom says. “Most of the procedures are documented in ISO 14644-3, [but] certification can mean many things to different entities based on their contractual obligations to their customers. This is why you will find many statements throughout the testing standards and practices referring to the agreements between the certification supplier and end-user, superseding the actual standard or practice. Having said that, when it comes down to classifying a room, you will pass or fail based on airborne particle concentrations.”

Dan Milholland of Milholland & Associates, Holly Springs, N.C., who is also a member of NEBB’s 2012 cleanroom committee, offers another definition.

“Currently, IEST-RP-CC-06 Testing Cleanrooms and IEST RP-CC-34 Testing HEPA and ULPA Filters and the NEBB Procedural Standards for Certified Testing of Cleanrooms are the best documents to follow for cleanroom testing,” he says. “Meanwhile, ISO 14622 Cleanrooms and Associated Controlled Environments - Part 3 - Test Methods is under revision. The current version is rather confusing.”

Who can certify a cleanroom?

The NEBB certifies firms, professionals, and technicians under its CPT program, which entails stringent requirements (box, page 10). The NEBB website ( and the Controlled Environment Testing Association website ( both offer search engines for finding certifiers. However, organizations looking to hire a certifier should check references and ask pointed questions.

“Not all cleanroom certifiers are equal in ability,” cautions Milholland. “The only ‘certifications’ for certifiers are S2C2 in the U.K. and NEBB in the U.S.A. The NEBB program is very, very demanding and is valued internationally.”

“You should hire a legitimate cleanroom certification firm,” Hocom says. “Make sure that they are using calibrated equipment, carry insurance, etc. There are plenty of firms out there that say they are cleanroom certifiers when actually they just farm the work out to an individual who rents equipment for projects. Companies should ask a few questions such as ‘Do you subcontract this work or do it yourself?’ when attempting to secure a certification firm. Just [practice] due diligence in order to weed out the pretenders.”

A certifier should be a neutral third party, not someone working for a construction company, adds Hocom. “I am always a bit confused as to why some end-users are O.K. with cleanroom construction contractors providing their own certification. ‘We certify that we built what we said we would. Now pay us.’ There is really no more of a ‘fox checking the henhouse’ scenario.”

“To be most effective, the certification contractor should work directly for the owner,” agrees Milholland. “He is the extension of the owner’s QA staff during and after construction. The farther removed from the owner, the more the cost with less and less input to the project.”

Bring in a certifier from the beginning

A certifier can be brought in at the design stage so potential problems can be fixed before construction. “When a company determines they need a cleanroom to enhance the quality of their product, they should consider bringing a qualified cleanroom certification contractor on board early in the process,” says Milholland. “The cleanroom design should be reviewed to assure testing has been considered. Are aerosol challenge test ports available to measure challenge concentrations before the HEPAs? Does an air handler supply air to both filtered and non-HEPA filtered areas? Is the cleanroom positive to all surrounding areas, including the ceiling? Are room returns spaced adequately to provide proper airflow patterns within the clean space?”

A qualified outside company can also improve the client’s bidding process and clarify liabilities, says Milholland. “The certification firm can help develop and/or review the appropriate contract documents before going out to bid. The testing methodology and acceptance criteria should be clear to all contractors bidding the job. Define responsibilities for non-conformance. If the filters leak, does the repair/replacement/retesting fall on the filter manufacturer, trucking company, installers, or the mechanical contractor?”

Certifiers continue to play a role during and after construction, conducting pressurization and other tests to determine whether systems meet design specs and current standards. Depending on the facility’s age, certification may test the cleanroom “As Built” (newly constructed and unoccupied), “At Rest” (already functional but currently unoccupied and with processes shut down), or “Operational” (measured with people, processes, and tools functioning fully).

Certifiers may also assist in staff training and should be able to provide operator manuals for equipment if needed, or order missing/malfunctioning parts if a piece of equipment is not functioning properly.

DIY? Probably not

Cleanroom certification can be done in-house, but it’s not an inexpensive proposition. Typical equipment includes a capture hood or air velocity meter for an airflow velocity check; an aerosol generator, challenging agent, and photometer for the HEPA filter integrity test; a pressure differential gauge for measuring room pressure differentials; a temperature and relative humidity meter; and a CFM particle counter. Rental costs can total around $3,000 per week; purchase costs may be $10,000 or more, with the added annual expense of calibration. Many building owners lack properly qualified staff, even if equipment is available.

Thus experts suggest that it’s best to leave certification to the pros. “Testing a cleanroom does not fall under the ‘cheap labor’ category,” Hocom says. “The cleanroom is the heart of the profit center, and certification for a lot of these smaller companies is their main source of quality control. This not an area to skimp on, especially when you can amortize the cost over a 12-month period. Certification will probably fall somewhere between the costs of coffee and toilet paper on the profit and loss [statement].”

Do’s and dont’s

Once you’ve decided to hire professionals, Hocom says, it’s best to trust their guidance. “There is a strong tendency for the end-user to play ‘shoot the messenger’ when things are not testing well. It is important for the end-user to understand that the certification contractor is providing data and not opinion. No matter how big of a headache being out of compliance may be, beating up the certifier is just counterproductive.”

Milholland agrees that, to avoid conflict, the certifier’s word should be final, and the certifier’s expertise should guide other contractors involved in construction and testing. “The cleanroom certifier’s instrumentation is the ‘gold standard’ for the project. Air balancing contractors and the certifier should perform a head-to-head comparison of test instrumentation before the beginning the final balance. If the comparison data is not identical, a K-factor should be developed and applied to the balancing contractor’s instruments.”

Once a cleanroom is certified, the building owner should maintain it properly and have it re-certified as required. Procedures and schedules will vary based on cleanroom Class designations, ranging from a monthly analysis to annual or biennial checks. Whatever the timeline, it’s imperative to stay on top of things.

“End-users should not allow their cleanroom to degrade,” says Hocom. “When problem areas are revealed during the certification, they should be addressed and not left to reveal the same result the following year. One problem usually will breed another and another until the cleanroom fails certification. Then we are back to ‘shoot the messenger’ and the ultimate plight of a cleanroom certifier.”

Who Certifies The Certifiers?

The National Environmental Balancing Bureau is the recognized professional organization that accredits companies and individuals involved in cleanroom certification. For a company to earn Certified CPT (Cleanroom Performance Testing) Firm status from the NEBB, it must keep records of responsible performance; own a complete set of instruments that are required to perform certification tests in the various disciplines; and have at least one NEBB Certified CPT Professional as a full-time employee in a management position.

A Certified CPT Professional is a full-time employee of a Certified Firm in a management position who has passed the professional-level written and practical qualification exams, and meets ongoing recertification requirements. CPT Professionals must have practical working knowledge, be able to make sound technical decisions, and demonstrate proficiency in the use of relevant instruments.

A Certified CPT Technician is a full-time employee of a Certified Firm who has met the technician-level experience requirements of NEBB and has passed technician-level written and practical qualification exams. A CPT Technician must be supervised by a CPT Professional, although “supervision is not intended to infer constant oversight.” CPT Technician status is maintained by continued employment with a Certified Firm.

MaryBeth DiDonna is the Managing Editor of Controlled Environments.

This article appeared in the January 2013 issue of Controlled Environments.