The Bottom Line on Buying a Cleanroom System
By: Rick Dobson
October 2009
What questions, as a potential buyer, do you need to ask to ensure your
performance specification will be met?
You have been tasked by senior management to look into purchasing a cleanroom
environment for a possible new product line. The mandate is that the cleanroom
system provider must guarantee temperature, humidity, pressurization, and
classification. As with any purchase, it is always best to be an educated buyer and
have researched the options available to you. Knowing what questions to ask and
what the cumulative effect is to those answers will make for a sound decision process
and an overall successful project.
As a cleanroom buyer, the first question should be “what information, as the owner,
will I need to provide the cleanroom contractor to ensure compliance with my
cleanroom requirements and to get a performance guarantee?” And remember a
guarantee implies meeting specific documented standards — data provided by you.
The more specific you can be with your design criteria information the better. This
does not mean that you have to do the detailed design but rather you are providing the
benchmark requirements that need to be achieved in the design and that will
eventually become part of the contract documents.
This simple four step process will help cleanroom buyers with design criteria
questions, mechanical equipment selection, and cleanroom testing to achieve your
cleanroom design performance guarantee.
Step 1: Determine your specific cleanroom requirements for temperature,
humidity, pressurization, and cleanliness.
The answers you provide to these questions can have a dramatic effect on the
operational requirements of the cleanroom, cost of the mechanical equipment, and
long term facility operational costs. When providing your operating conditions, be
specific. Don’t give a wide range of operation if it’s not required. The more specific
you are with your operating ranges for temperature and humidity, the tighter the
system can be designed, eliminating unneeded additional capacity and keeping the
mechanical costs in check. Additional capacity engineered into a project as a result of
erroneous or undefined information has a cumulative effect on equipment sizing that
will ultimately be a detriment to the project budget and operational costs.
Typical temperature designs will be in the range of 68 – 72°F year round. This is a +/5 degree uniformity specification. In most instances this is an acceptable operating
temperature range for personnel comfort within the cleanroom. You may need to look
at specific temperature requirements depending on your gowning protocol or
temperature uniformities that are driven by your specific product manufacturing
requirements. Think of the cleanroom in terms of zones and determine the
temperature ranges for each of the zones remembering that each different temperature
zone may require additional mechanical equipment, controls, and ultimately more
cost. Cleanrooms with large equipment loads may require a different zoning approach
and would require additional review.
Humidity requirements are most often product driven and can cover a wide range of
operation. The biggest problem I see is over-specified humidity control due to the
unknown requirements of the manufacturing process. Humidity control can add a
tremendous amount of money to your design and operating costs, so again be as
specific as possible and understand the cost implications of specifying a humidity
range that is not needed. For example:
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Ambient to 60% RH maximum is a standard design with RH control utilizing
the air handler cooling coil.
60% RH year round means summer conditions can be maintained utilizing the
cooling coil; winter conditions will require additive humidification.
30% to 60% RH year round is considered a wide range operation and requires
the room to operate within these conditions at anytime. The lower RH
condition will drive the design to utilize specific dehumidification beyond that
of the cooling coil and additive humidification for the higher RH levels.
If your product is extremely temperature or humidity sensitive you may have
to tighten the uniformity requirements.
Pressurization cascade can be positive or negative to the surrounding ambient area
dependent on the specific manufacturing requirements. The pressurization
requirement is a factor of the products manufactured within the cleanroom and also
personnel safety. To maintain pressurization will require conditioned make-up air at a
percent of the total airflow requirement to offset exhaust and designed leakage rates.
Negative pressure cleanrooms are typically designed with filtered returns such as bagin/bag-out filtered return air or as once through systems and are the most expensive to
operate because all of the conditioned cleanroom air is fully exhausted continually.
Classification requirements are again most often product driven through approved
manufacturing guidelines. You will need to research your specific manufacturing
cleanliness requirements to create your user requirement specification (URS). When
specifying your cleanliness levels make sure to indicate your testing requirements 1)
at rest, 2) in operation, and 3) other. With most cleanroom operations, the majority of
particulate is generated by personnel working within the room. It’s important to
review the number of people that will be working in the cleanroom, the gowning
protocols, and the number of people per shift or the number of hours of operation per
day. It’s not uncommon for room cooling loads to actually drive the air change rates
within a cleanroom. If your manufacturing guideline recommends 60 ACH and the
design engineer comes back with a higher air change rate, it’s probably due to the
room cooling loads — but do ask for an explanation.
How do you control temperature/humidity/pressurization and what data do you need
for your validation process? Control systems can go from basic to complex in a hurry
and the cost escalation can be alarming. As an owner, you need to discuss what type
of control and monitoring will be required with your manufacturing group. A stand
alone control system is normally the least expensive with localized indication of
temperature, humidity, and pressurization. These controls can accommodate a 4-20
ma output for localized alarm indication. At the other extreme are full building
management systems (BMS) with fully validated points of control, remote monitoring
capability, and compliance with Title 21 Code of Federal Regulations (21 CFR Part
11).
Step 2: Develop a dimensioned layout drawing of the cleanroom area, paying
specific attention to your product flow, personnel flow, process equipment
layout, process utilities, electrical requirements, and maintenance access.
Remember to include personnel and material airlocks as required. Again, this is an
area where you need to do your homework. More often than not you see cleanrooms
that were not designed for adequate product and personnel flow creating
manufacturing problems along with operational problems when return air drops are
blocked with materials.
Ceiling heights are often driven by the process equipment within the room and can
vary widely depending on the manufacturing process. The cost of a cleanroom is
largely in the mechanical equipment. The airflow requirements (CFM) are determined
by the volume of the room which is a direct correlation of the room height (length x
width x height = ft/3 of volume). To minimize the cleanroom volumetric airflow
requirements, keep the ceiling levels to a minimum and utilize soffit details when
possible.
Return air details are typically utilized in Class 10,000 (ISO 7) and cleaner
environments. Remember to allow dimensionally for return air locations in your
overall space planning layouts. The quantity of low wall returns will ultimately be
determined by the cleanroom classification and room sensible/latent load
requirements to achieve the needed air changes per hour (ACH) and temperature
uniformity. Allow enough room in your layouts to keep the return air depth such that
the feet per minute velocity (FPM) is within good engineering practice standards.
Going outside the recommended velocities can result in poor room performance and
excessive air noise.
Architectural finishes and clean details are typically driven by the specific
manufacturing process. A good reference to utilize is the ISPE Baseline
Pharmaceutical Engineering Guide. These types of reference materials will guide you
in the accepted materials of construction. Ensure that all of the architectural finishes
are compatible with your cleaning solutions and will withstand your long term
cleaning protocols.
Step 3: Review your mechanical support services and determine your preference
on providing conditioned air to your cleanroom.
It’s also important to consider the location of the mechanical equipment in relation to
the cleanroom.
If you have an existing building chiller and the chiller capacity is adequate and the
chilled water temperature and GPM work for the design, this may be a possible area
for cost savings. One thing to remember is that the cleanroom is now tied to a
building chiller and if the chiller goes down so will the cleanroom. A dedicated
mechanical system packaged chiller, packaged DX (Direct Expansion) system, or split
system has the advantage of being a standalone system and not tied to the existing
HVAC system, however, the upfront and long term operational costs are generally
higher.
Air handlers are available in standard configurations which might again be an area of
savings but typically cleanroom air handlers require custom construction materials,
CFM requirements, pre-heat, re-heat, and dehumidification.
HVAC equipment locations for cleanrooms can be located indoors or outdoors.
Indoor air handling units (AHUs) are less expensive than equivalently designed
outdoor equipment. The down side to indoor equipment is space allocation and
possible noise implications. Outdoor units are a standard design but will require curbs
to be roof mounted and pads for ground located equipment. If you have a leased
building, the location of the equipment needs to be discussed with the owner of the
building as most leased spaces require all equipment to be removable at the end of the
lease.
Step 4: Finalize your user requirement specification (URS) to be presented to the
cleanroom contractor.
You don’t want to limit the ability of the cleanroom engineer to design the cleanroom;
however, you do need to provide your design criteria in a clear and concise document
that leaves no room for interpretation. As part of the specification, require a copy of
the turn-over package and copies of all test reports as noted below.
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Provide a written specification with the design criteria for temperature,
humidity, pressurization, and cleanliness.
Provide a dimensioned layout drawing showing your process flow.
Be prepared to discuss your HVAC preferences and equipment locations.
Provide any personnel, process, and exhaust sensible and latent loads.
Provide a preliminary control strategy and your monitoring requirements.
Provide a detailed testing strategy and as a minimum include:
Temperature control and uniformity
Humidity control and uniformity
Pressurization verification
Particulate counts
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Request copies of the Installation Qualification and Operational Qualification
reports.
Request site test reports from a certified testing and balance company.
Request copies of the HEPA filter factory and site certification reports.
Request a list of each of the HEPA filter serial numbers and their installed
locations within the project.
The narrative above is a brief example of the initial information required to start the
design for a cleanroom environment. There are additional design factors that need to
be considered before entering into the detailed design phase. Your cleanroom
contractor will ultimately need to review the constructability of your design criteria
requirements to provide a performance guarantee.
Rick Dobson is Director of Pharma Sales for AES Clean Technology in Suwanee,
Georgia, and can be reached at 678-804-0260 x12 or rdobson@aesclean.com.