C4: Critical Cleaning For Contamination Control: Where Does Your Management Get Its Information?

By: John Durkee, Ph.D., P.E.
October 2009

This is a column about the role of information in risk management. If your managers read, this column applies to YOU...

In the longtime favorite TV series Boston Legal, the closing courtroom scene with attorney Alan Shore was always the climax. And in that climax, Shore would inevitably rant in support of his weekly tilt at windmills that everyone knew that “studies show...” one compelling thing or another.

Well, since we probably haven't read and perhaps wouldn’t understand, those “studies,” just where do we (and imaginary characters like Alan Shore) get the information which supports our views (and those of the writers of shows like Boston Legal)?

WITHER GLYCIDYL METHACRYLATE?
Back in the 1970s at a chemical plant, I was responsible for coordinating a full-scale plant test in which a copolymer would be made using the monomer glycidyl methacrylate. At the time we were all learning about the science associated with cancer. Professor Bruce Ames had just published his groundbreaking paper which claimed that carcinogens were mutagens. And glycidyl methacrylate had just flunked Ames’ test: the chemical caused bacteria to mutate.

My managers nearly went ballistic! They had read in the press that 80% of the chemicals which flunked Ames’ test were actually carcinogens, and some thought carcinogens were “super-toxic” chemicals which killed after a single exposure.

A lot of explaining was necessary to justify that plant trial.

WITHER TOXICOLOGY?
STATS, a nonprofit, nonpartisan research organization affiliated with the George Mason University, and the Society of Toxicology (SOT), the professional association of that scientific discipline, recently conducted a telephone survey of the Society’s approximately 3,600 members; about 1,000 members responded. The survey results were released at the National Press Club in Washington on May 21, 2009.

The purpose of the survey was to learn whether toxicologists believe that the media is providing the same perspective to readers and viewers as held by professional toxicologists.

There was a clear outcome: toxicologists responding to the survey overwhelmingly said they believed that the media does a poor job covering basic scientific concepts and explaining risks of managing chemicals.

SURVEY SAYS...
Toxicologist respondents overwhelmingly rejected the notion that exposure to even the smallest amounts of harmful chemicals is dangerous or that the detection of any level of a chemical in your body by biological monitoring necessarily indicates a significant health risk — views often found in print.

The clear theme of the survey outcome is that toxicologists believe that risk in managing and using chemicals is overstated. Table 1 shows how SOT members believe the pronouncements of various organizations unscientifically overstate chemical risks.

Being noted for exaggeration isn’t a recipe for credibility. Only 15% or fewer of the approximately 1,000 survey respondents describe as accurate the overall portrayals of chemical risk specifically found in The New York Times, Washington Post, and Wall Street Journal. “New media” is thought by professional toxicologists to more accurately represent the overall risks about chemicals, with Wikipedia at 21% and WebMD at 29%.

IF IT BLEEDS, IT READS
Should this be surprising? In a sense, no. Newspapers (and TV) have long believed bad news sells newspapers. And advocacy organizations are not representing their members if they undersell anything similar to their named point of view. It is not their job to be fair, but to agitate for “change.”

SCIENCE IS ABOUT CONSENSUS
A fundamental tenet of toxicology is that “the dose makes the poison” — that is, if you take enough of anything, it can harm you. Three out of four toxicologists responding to the survey complain that news organizations don’t know or accept that in their writing and editing. More than 95% of SOT members responding to the survey believe the media poorly understand absolute vs. relative risk, can differentiate correlation from causation, good studies from bad studies, and especially that it isn’t one study which makes science — it’s the consensus of nearly all about all studies!

We who manage chemicals in cleaning or other operations probably understand the point of view of toxicologists. But those who observe, use, regulate, and manage our activities almost certainly don’t if they get their information from news sources. What can we do about that?

Contamination Control In And Out of the Cleanroom: Trapping Airborne Molecules: Molecular Filters, Gas Purifiers - Part 1

Contamination Control In And Out of the Cleanroom: Trapping Airborne Molecules: Molecular Filters, Gas Purifiers - Part 1
By: Barbara Kanegsberg and Ed Kanegsberg
October 2009

“AMC filters don’t work.” “We don’t need to trap AMC’s.” These facile sentiments impede progress in critical applications.

Certainly, being proactive with Airborne Molecular Contamination (AMC) is essential. Understanding, detecting, and eliminating or reducing AMC sources should be the first line of defense.¹ Sometimes, however, AMC must be trapped; you have to “head it off at the pass.” Successful removal of molecular contamination from air and gas streams requires knowledge of the chemical nature of the contaminating molecules.

Why are AMC trapping devices not ubiquitous? The field of molecular filtration and purification is still emerging from the shadow of emphasis on particle control. Further, many industry sectors still do not fully appreciate the importance of molecular level process control and the distinctions between particle removal and molecule removal.

While specific applications are distinct, AMC removal and gas purification, including the preparation of Clean Dry Air (CDA), have many common processes and suppliers. Both involve removal of unwanted molecular species before they reach the surface of the product.

MOLECULAR REMOVAL IS MORE COMPLEX THAN PARTICLE FILTRATION
For particles, the primary discriminator is particle size. A particle filter acts somewhat like a window screen to let small particles and gases through and block larger particles. Granted, High Efficiency Particle Air (HEPA) filters are more complex than a window screen, and they can trap or impede particles both larger and smaller than the pore openings between filter fibers. However, standard HEPA filters do not remove molecular contaminants that are several orders of magnitude smaller than the size rating for a HEPA filter. For AMC filtration, rather than removing contaminants on the basis of size alone, the chemical nature of the contaminant becomes very important.

TERMINOLOGY
The fact that molecular filtration is much more complex than particle filtration is reflected in the terminology. The terms filtration and purification are both widely used; some experts are adamant about the appropriateness of one term over another. Some use filters for devices that physically separate gas components but do not change their chemical nature as distinguished from purifiers for devices that alter the chemical being removed. We tend toward the view² that a filter is a device to perform purification. Other terms, such as trap, sieve, desiccant, or getter, may be used to describe certain filtering or purification functions.

STANDARDS
ISO 14644-8, a more encompassing descendent of the SEMI F21-1102 standard, creates eight categories for molecular contaminants (Table 1). The categories reflect different mechanisms by which contaminants can be damaging to a product.

It is noteworthy that the Institute for Environmental Sciences and Technology (IEST) has recently released a first-edition document³ that provides guidelines on the design of filter systems to eliminate trace amounts of AMC.

FILTER LIFETIMES
Those who have worked with HEPA filters exclusively require a paradigm shift in managing AMC filters or purifiers. A properly installed HEPA filter, with appropriate pre-filters, has a very long lifetime. The energy needed to force air through a HEPA filter increases with use. This can be monitored by tracking the pressure drop through the filter and provides a metric to determine when energy costs make replacement economical. In addition, if the pressure drop gets too large, seals can fail and unfiltered air bypasses the filter.

In contrast, most molecular filters or purifiers are consumables with finite lifetimes. With many, there is little or no indication of loss of efficiency. An AMC filter or gas purifier may maintain the design level of efficiency until essentially all active sites have been exhausted, at which point the device rapidly stops working. Therefore, most users employ a periodic replacement schedule.

APPLICATIONS
Applications for molecular filters or purifiers are quite varied. Many of the most stringent requirements still come from the semiconductor and related industry areas such as photovoltaic devices. However, there is increasing interest in other critical applications such as aerospace and precision optics. Examples include prevention of degradation of surfaces that are to be joined or coated and control of outgassing into confined spaces. Additional perhaps non-traditional applications for AMC filtration/purification include conservation of art and documents, and achieving good indoor air quality and odor control in schools, commercial buildings, and airports.

Some purification systems not only provide high degree of purification but also include a method for certification of purity of either CDA or of an individual gas. One system⁴ contains four sampling traps. The gas to be certified is drawn through a set of three traps/purifiers/filters to respectively trap acids, bases, and hydrocarbons/refractory gases. The traps are subsequently submitted for analysis, the acid and base traps by ion chromatography and the hydrocarbons/ refractory gases by thermal desorption gas chromatography. Analysis of the control filter/trap, installed downstream of the first set of traps, allows the determination of the percent of capture. For example, if the first set of filters trap all impurities, the control would analyze as “empty.”

MOLECULAR TRAPPING MECHANISMS
Molecular trapping devices do work. However, it is essential to select the appropriate trapping device and to establish and conduct a maintenance/replacement schedule.

Given the diverse nature of molecular contaminants, there is no universal AMC filter or purifier.

Next month: We will look at several mechanisms for filtration or purification.

Acknowledgements
The authors acknowledge the helpful comments of Mike Hoke, Matheson Tri-Gas, Inc.; Cristian Landoni, SAES Pure Gas, Inc.; Mark Stutman, Camfil Farr; and Gerald Weineck, Donaldson Company, Inc.

References

1. B. Kanegsberg and E. Kanegsberg, “Contamination Control In and Out of the Cleanroom.” Controlled Environments Magazine, June, Jul/Aug., and Sept. (2009).
2. G. Weineck, Donaldson Company, Inc, personal communication.
3. “Design Considerations for Airborne Molecular Contamination Filtration Systems in Cleanrooms and Other Controlled Environments”, IEST-G-CC035.1, available through www.iest.org.
4. C. Landoni, SAES Pure Gas Inc., personal communication.

Gaseous Decontamination for Critical Environments

By: Jim Polarine and Claire Fritz
October 2009

Hydrogen peroxide vapor systems can address large scale contamination challenges.

Fogging and gaseous decontamination become options when facilities are going through large scale bioburden outbreaks, or are bringing an area up after a shut down, a hurricane, a power failure, or construction events. The majority of the systems used for fogging and gaseous decontamination applications use EPA registered sterilants as an adjunct to cleaning and disinfection. Some facilities pre-clean surfaces with surfactant-based disinfectants and then fog the area with a sporicide such as 3-6% hydrogen peroxide or hydrogen peroxide/peracetic acid blends.

Typical fumigation or gaseous decontamination methods are dry processes that penetrate HEPA filters and can reach areas that are not easily reached by manual disinfection or fogging. These methods can also be validated and challenged with 106 biological indicators to confirm microbial kill. However, the HVAC system to the cleanroom must be shut down before decontamination and the area must be well sealed. Paraformaldehyde is an effective, low-cost fumigation agent, but is a human carcinogen and leaves a residue after the process. Chlorine dioxide gas, another option, is an excellent sterilant, but it has very low allowable human exposure limits (0.1 ppm OSHA TWA; 0.3 ppm STEL); so it is very critical that the space be thoroughly sealed before fumigation. Hydrogen peroxide vapor is rapidly emerging as an excellent alternative for large volume critical environments because it is easy to contain, is non-carcinogenic, leaves no residue, and is environmentally friendly due to its decomposition into water vapor and oxygen.

Sporicidal concentrations of hydrogen peroxide vapor at ambient temperature are approximately 0.1 - 2 mg/L (70-1400 ppm) depending on the volume. The amount of time that is required to kill 90% of a microbial population at a specific concentration is defined as the decimal reduction value (D-value). One D-value is equivalent to one log of spore reduction. Hydrogen peroxide vapor produces shorter D-values for Bacillus subtilis than both paraformaldehyde and ethylene oxide at optimum sterilization conditions.¹ Geobacillus stearothermophilus shows the highest level of resistance and is most frequently used as the challenge organism in validation.²

The shortest D-values are generated when the hydrogen peroxide vapor concentrations are the greatest. Figure 1 demonstrates D-value versus hydrogen peroxide vapor concentration. A 35% hydrogen peroxide liquid is flash-vaporized to generate a gaseous mixture of both water and hydrogen peroxide. While concentration is the primary variable, humidity and total saturation also impact the rate of microbial kill. Figure 2 represents a graph of D-value versus saturation for a constant hydrogen peroxide vapor concentration.

Because the hydrogen peroxide vapor concentration is dependent upon temperature and humidity, the surface temperatures and the relative humidity inside the room will determine the injection rate that will produce the optimal concentration. Vapor condensation should only occur if the injection rate is too high for the temperature and humidity of the room. With the hydrogen peroxide and water vapors below the dew point and noncondensing, exposure conditions will remain uniform and corrosion should not occur on any exposed equipment or surfaces.³ This process is defined as a vapor because hydrogen peroxide’s state at ambient conditions is a liquid; however, this does not imply that hydrogen peroxide cannot remain in a dry, gaseous state

Hydrogen peroxide vapor systems were first commercialized as portable generators in the early 1990s and were utilized specifically in isolator applications for sterility testing and aseptic processing. These systems are completely self-contained and easy to integrate into existing applications but can be limited in capacity. Small cleanroom applications, such as at Pharma Hameln GmbH, began in the mid 1990s. A portable hydrogen peroxide vapor system was installed and validated for the decontamination of an aseptic filling room. The 56-cubicmeter (1970-cubic-foot) room was decontaminated in two hours and then aerated in four hours.⁴

The first integrated, non-portable system became available in the late 1990s. Although these units require an external dry air source and integration into a facility’s HVAC system, they can operate continuously. Figure 3 demonstrates a typical setup for an integrated hydrogen peroxide vapor system for a cleanroom application.

The newest integrated hydrogen peroxide vapor systems now offer almost four times the vaporization capacity of the portable units and much greater air flows, so these systems now have the capability to efficiently decontaminate large volume cleanrooms. Facilities can now plan for the future and install a hydrogen peroxide vapor system as a built-in utility for high-level room decontamination as an adjunct to normal manual disinfection methods, and to drastically reduce bioburden during a shutdown or after new construction and renovation.

Hydrogen peroxide vapor can also be used as a high-level decontamination method for critical items and equipment that need to be brought into a classified environment. These gaseous systems can be built into airlocks or pass-through chambers for an automated and validated equipment decontamination process. However, cycle times can be one to two hours depending on the application, so the use of liquid sporicides may still be the best option for decontamination of items if there are time constraints.

A complete solution for microbial control within a cleanroom should include chemical technologies and processes for varying levels of contamination and all types of surfaces found in the space. This includes formulated chemistries for manual cleaning and disinfection, combined with a high-level gaseous decontamination method for the large-scale contamination challenges that can be expected to occur over the lifetime of a critical environment.

References

1. Klapes, N.A. “New Applications of Chemical Germicides: Hydrogen Peroxide.” Program and abstracts of the ASM International Symposium on Chemical Germicides, American Society for Microbiology, 1990.
2. Kokubo, M., Inoue, T., and Akers, J. “Resistance of Common Environmental Spores of the Genus Bacillus to Vapor Hydrogen Peroxide.” PDA Journal of Pharmaceutical Science and Technology, May, 1998.
3. Hultman, C., Hill, A. and McDonnell, G. “Physical Chemistry of Decontamination with Gaseous Hydrogen Peroxide.” Pharmaceutical Engineering, January/February 2007.
4. Jahnke, M. and Lauth, G. “Biodecontamination of a Large Volume Filling Room with Hydrogen Peroxide.” Pharmaceutical Engineering, July/August 1997.

Jim Polarine is a technical service specialist at STERIS Corporation. He has been with STERIS Corporation for over eight years, where his current technical focus is microbial control in cleanrooms and other critical environments. He is a frequent industry speaker and has worked on several books and article publications related to cleaning and disinfection and contamination control.

Environmental Conciousness in Cleanroom Consumables Selection and Use

By: Duane Webb
October 2009

How can the expectations of natural resource conservation and waste elimination be achieved in highly critical cleanroom manufacturing environments?

Environmental responsibility is no longer just an occasional headline in the news. It is expected socially and often mandated governmentally. Every day the public is demanding a decreased impact on the environment and an improvement to their quality of life globally. Every day new environmental regulations are introduced and government agencies are mandating change. In response, companies are announcing or improving “green” or “environmental responsibility” programs as their commitment to creating a better world. Initiatives to conserve our natural resources, eliminate operational waste, and produce more environmentally-friendly products are now both a corporate and customer expectation.

This article will focus on cleanroom consumables in the form of cleanroom wipers with a brief discussion included on cleanroom bond. The concepts of reduce, reuse, recycle, and biodegradability will be presented along with how to apply these concepts in cleanroom wiper and bond selection for reduced environmental impact. The most common cleanroom wiper materials will be presented with information about biodegradability or recyclability. Also, included will be product alternatives and methods of use that can lessen the overall consumption of wipers and limit the depletion of natural resources, such as high performance product selection and alternative packaging configurations. The article will further discuss pre-wetted wipers and their impact on volatile organic compound (VOC) emissions and alcohol solution waste. In closing, wiper options will be presented that reduce landfill impact through higher degrees of biodegradability when recycling is not an option.

UNDERSTANDING THE WASTE MANAGEMENT HIERARCHY
The waste management hierarchy is composed of three guiding principles: reduce, reuse, and recycle.

Reduce: To minimize environmental impact and produce less waste by purchasing more environmentallyfriendly products and improving methods to lessen consumption. Examples would include lighter weight, high absorbency wipers, and packaging configurations that use less packaging material.

Reuse: To use an item over and over prior to recycling or land filling. This is rarely done with cleanroom wipers due to the critical nature of the process and material requirements; however, there are some instances of reuse in less critical environments dependent on the ability to remove the contamination added by the original cleaning process.

Recycle: Recycling is the primary component of modern waste management and involves the collection and processing of used materials to produce the same or a new product. Leading examples include the recycling of corrugated and plastic packaging materials.

Implementation of any of the above three concepts will result in the following:

• Less waste of potentially useful materials.
• Conservation of natural resources that would be required to produce new materials.
• Reduced energy usage that would be required to produce new materials.
• Reduced air pollution.
• Reduced water pollution.

Once the three principles of the waste management hierarchy have been applied, the remaining waste must be incinerated or disposed of in a landfill. The landfill impact can be minimized by using materials that are biodegradable in municipal or commercial composting facilities.

Biodegradation: Is the process by which organic material substances are broken down by the enzymes produced by living organisms. Wipers made from natural fibers biodegrade while wipers made from synthetic fibers like polyester and polypropylene are almost impervious to biodegradation. In the case of blended wipers, the portion of the wiper composed of natural fibers will biodegrade, offering a degree of biodegradability.

RECYCLABILITY AND BIODEGRADABILITY OF COMMON CLEANROOM MATERIALS
Let’s look at the recyclability and biodegradability of common cleanroom wiping materials, packaging components, and cleanroom bond paper.

Synthetic Fibers or Yarns: The most common synthetic fibers or yarns used in wiper fabrics are polyester, nylon, and polypropylene. These materials are petroleum based and are all almost impervious to biodegradation and are not renewable.

Cellulosic Fiber: Cellulosic fibers are natural fibers sourced from wood and are biodegradable. Depending on the wood pulp source, the fibers may be renewable and sustainable. The most common of these fibers found in wiping materials are cellulose (pulp), abaca, and soft wood.

Cotton Fibers or Yarns: All cotton fibers are 100% natural and are biodegradable. Cotton is also renewable and sustainable.

Regenerated Cellulose: These are cellulosic fibers that are regenerated through a special chemical process. The most common of these fibers found in cleanroom wipers are lyocell and rayon.

Corrugated Cartons: Corrugated cartons are biodegradable; however, due to the abundance of corrugated materials in the market, corrugated cartons should be recycled.

Plastic Bags or Pouches: The plastic bags currently used for cleanroom wipers are typically not biodegradable; however, once again due to the abundance of these materials in the market, the type of plastics used can be recycled.

Plastic Canisters: The plastic canisters typically used for cleanroom wipers are not biodegradable; however, they are often reused and can most likely be recycled.

Cleanroom Bond Paper: Cleanroom bond paper is made of cellulosic fibers which are biodegradable; however, a large majority of the cleanroom bond paper on the market is impregnated with a synthetic latex (to reduce fibers) which negatively affects the biodegradability and the recyclability. Cleanroom bond papers without the latex impregnation are biodegradable and recyclable.

MINIMIZING IMPACT THROUGH PROPER SELECTION AND USE
Now that we understand the waste management hierarchy, biodegradation, and the recyclability and biodegradability of common cleanroom materials and packaging, how do we apply this knowledge to minimize environmental impact when selecting and using cleanroom wiping materials and cleanroom bond paper?

Evaluate and choose the optimum packaging configuration.
Cleanroom wiping materials can be purchased in multiple packaging configurations. The best way to minimize the impact on the environment is to choose packaging configurations that contain the most wipers per carton or plastic bag or pouch. In this way, the amount of natural resources and energy used to produce those materials along with the amount of material to be recycled and the energy required for recycling is lessened.

Choose a wiper with higher absorbency.
When comparing wipers of the same material type, size, basis weight, and general cleanliness performance for spill pick-up or other similar types of applications, look at absorbency values. By choosing a wiper with higher absorbency, the amount of wipers required can be minimized.

Choose a wiper or bond paper with a lower basis weight.
When comparing cleanroom wipers or cleanroom bond paper of the same material type, size, absorbency and general cleanliness performance, look at basis weight. By choosing a wiper or bond paper with a lower basis weight, the amount of natural resources and energy required to produce the wiper are reduced and the weight of material that may be placed in landfills post use is reduced.

Be sure that operators are trained in proper wiper usage and cleaning techniques.
The use of improper wiping techniques can lead to increased wiper usage, increased solution usage, and decreased process and product yields. All of which lead to an increase in natural resources and energy consumed in manufacturing and an increased amount of material to be recycled or sent to landfills. Most leading cleanroom wiper manufacturers have produced cleanroom wiping guides for reference or can provide operator training in proper techniques as part of their technical service programs.

Evaluate the use of pre-wetted cleanroom wipers in place of in-house wetting techniques.
By utilizing pre-wetted wipers several environmental benefits can be derived:

• Reduced volatile organic compound (VOC) emissions: Many states, such as California, are now mandating reductions in VOCs and have put in place guidelines on the amount of VOCs allowable in products based on their intended use. Pre-wetted cleanroom wipers typically come in an easy to use re-sealable pouch that allows the extraction of one pre-wetted wiper at a time with very little VOC emission compared to in-house blending, spray bottles, and squirt bottles.
• Reduced solution usage: Alternative methods of wetting wipers in-house can lead to excessive solution usage. When using spray bottles or squirt bottles, the wiper can be over-saturated causing solution waste. There is also the waste associated with spills during in-house blending and spray or squirt bottle usage.
• Reduced process and product waste: Pre-wetted wipers ensure increased cleaning consistency and control due to very high wetting accuracy during manufacture and use. They can eliminate the potential for over-spray on sensitive parts when wetting dry wipers, thereby, increasing process and product yields, and reducing manufacturing waste.

CAN CLEANROOM WIPERS BE REUSED TO REDUCE ENVIRONMENTAL IMPACT?
To answer this question, we must first understand why cleanroom wipers are purchased. Cleanroom wipers are purchased to aid in the removal and/or control of contamination to levels that minimize the risk of process and product failure. They are primarily used in critical cleanroom environments where the purity of the wiping material and its overall performance characteristics are of extreme importance. Once the cleanroom wiper has been used in the cleaning process, laundering and returning the cleanroom wiper to anywhere near its original state would be extremely difficult. There is also the possibility that the re-laundered wipers could accidently migrate back into the critical areas and severely impact process yields and final product integrity. For these reasons, it is not recommended or a typical practice to reuse cleanroom wipers. With this being said, there have been instances where a very few companies have been able to reuse the cleanroom wipers for more industrial or lower grade applications reducing the purchase of those types of cleaning materials. This is dependent on the company’s capability to reduce or remove the existing contamination to a level required for those applications.

CAN CLEANROOM WIPERS OR CLEANROOM BOND PAPER BE RECYCLED TO REDUCE THE IMPACT ON LANDFILLS?
In their original state, prior to use, most cleanroom wiping materials can be recycled; this is practiced by some of the leading cleanroom wiper manufacturers as part of their environmental programs. Post use recycling efforts can be difficult due to the types of contamination now contained on the wiper in the form of oils, solvents, or sludges. The best source to identify whether the wiper material can be recycled post use is your current recycler of materials. In the case of cleanroom bond paper, products that are not impregnated with a synthetic latex can be recycled in the normal paper recycling program.

NOW THAT ALL WASTE MINIMIZATION OPPORTUNITIES HAVE BEEN EXHAUSTED AND THE ONLY OPTION LEFT IS THE LANDFILL, HOW CAN THE LANDFILL IMPACT BE LESSENED?

1. The first concern is to reduce the weight of the material that is going to be sent to the landfill. Hopefully this has been accomplished through the other waste minimization efforts that have been implemented. This is very important with knit cleanroom materials as these are exclusively made from petroleum based synthetic fibers that are almost impervious to biodegradation and is also important with latex impregnated cleanroom bond paper.
2. In the case of non-woven or woven cleanroom wipers and cleanroom bond paper, choose a cleanroom wiper or bond paper material that is biodegradable and that has all of the performance characteristics required to meet the process needs.
3. In the case of blended or bonded non-wovens, choose a cleanroom wiper that contains the highest amount of biodegradable material and that has all of the performance characteristics required to meet the process needs.

SUMMARY
Environmental consciousness and critical cleanroom consumables do not have to be mutually exclusive. With knowledge of basic waste management principles, the environmental properties of common cleanroom materials and proper cleaning methods, a significant reduction in environmental impact can be achieved. Further help in lessening the environmental impact of cleanroom consumable materials can also be sourced through cleanroom wiper manufacturers as part of their Cleanroom Wiper Usage Audit programs.¹

Reference

1. Webb, Duane. “The Cleanroom Wiper Usage Audit.” Controlled Environments Magazine, June 2009.

Nanotechnology Cleanroom - Design on A Dime

By: Raymond K. Schneider P.E.
October 2009

The tight budget of today’s nanotechnology facility start-ups makes the need for small scale cleanroom solutions as important as ever.

THE CHALLENGE
Over the past several years the term “nanotechnology” has been growing in the public consciousness. The science of small things holds the same allure that “microelectronics,” the buzzword of the 80’s, held at one time. Entrepreneurs see new generations of microelectronic devices, optics, pharmaceutical delivery systems, medical diagnostic devices, and an array of molecular level products about to breakthrough to the marketplace as “nanotechnology.”

Attend a nanotechnology forum or trade show and the exhibit floor is crammed with great ideas available for license or investment or partnering opportunities. What is rarely found is the much needed attention to detail regarding how the device is to be produced in a cost effective manner, to insure that initial investments are protected by profitable production. The requirement for a high production yield generally follows on the heels of the “gee-whiz” stage, characterized by “Wow, we did it....who woulda believed it possible?” First we invent/design, then we prototype, then we produce. Failure to produce economically carries the risk that others, who can produce at a profit, will be able to exploit the market window of opportunity.

As start-ups blossomed in “high-tech” corridors around the country a bit more than two decades ago, the search for product yield was a driver of cleanroom design and construction. Today the excitement of that era is returning through nano technology research and development. Not surprisingly, the manufacturing facility budget of today’s high tech nanotechnology start-up is as tight as the microelectronic counterpart of years ago. The requirement for cleanroom solutions “on a dime” is as important as ever.

Contaminants that negatively affect product yield can be particles or gases. The purpose of the cleanroom is to isolate the product from contaminants that cause product rejection by your quality control. This is done by keeping contaminants out of the facility or, should they enter, by removing them before they do damage. A variety of strategies are employed in large, well-financed facilities, but how does the start-up nanotechnology company, with relatively few dollars and many priorities, begin to address the need for an appropriate facility that will support small production runs of high quality, contaminant-free product?

FIRST STEPS
Assess the process to be contained within the space. While it might be convenient to house all phases of your process within a cleanroom, the size, hence cost, of the facility will immediately begin to grow. Identify those processes that must be conducted within a clean environment and limit this first clean area to only those process machines, WIP storage, materials, etc. necessary to support those processes.

Lay out the clean facility incorporating people and material flow and integrate it into the other, non-clean areas of the manufacturing facility that relate to the clean area. After careful consideration it may turn out that only a small percentage of the floor space needs to be cleanroom rated with the majority of the square footage being a “controlled environment,” that is, conditioned and maintained but not HEPA/ULPA filtered, and having only a modest air exchange rate.

Developing a “clean workspace” mindset is a challenge for those accustomed to working in an uncontrolled lab environment, however if cleanliness is critical to the end product the discipline associated with working clean is vital. A gowning protocol should be established, as should a janitorial protocol. By using cleanroom garments, you are protecting the product from the people. By regularly cleaning the cleanroom, in a meticulous manner, the debris that is inevitable in a workspace, and that in turn may become a product contaminant, is removed.

The cleanspace itself, whatever the size, should have walls, floors, and a ceiling (Figure 1) that do not contribute to the to particle count within the space, and are easily cleaned. A hard, cleanable floor, such as epoxy clad concrete or a seamless (if possible) sheet vinyl would be an appropriate floor surface. As part of the gowning protocol dedicated slip-on lab shoes would be helpful (shoe covers are good, too), as the floor will inevitably be the dirtiest area, and a major source of contaminating particles. Walls can be as simple as drywall or concrete block with an epoxy or polyurethane finish. The ceiling can also by drywall, though, depending on the application, an inverted “T” grid ceiling with non-shedding panels (such as those clad with high pressure laminate, aluminum, or vinyl sheeting) offers considerable flexibility. There are many materials that will suffice, but when cost is a key, simplicity in installation and maintenance is best.

NEXT?
After the appropriate sized space has been identified and a plan has been developed for the clean, easily maintained envelope, other key control parameters should be identified. It is advisable that these parameters be related to product yield requirements rather than some preconceived notion of how a “cleanroom” should perform, or designed around a specification that is not relevant to your product or your industry. There is no standard “nanotechnology” cleanroom particle count or critical particle size. There is a particle count and size appropriate for your product. Frequently, however, you will not know what it is.

Before you invest in a cleanroom, you should have a fairly good idea of your product’s “killer particle size” and how many of these particles you can tolerate within your cleanroom space. Whether you start with the gold-plated cleanroom or work your way up to it over time is a business decision you face. As a rule, the smaller the particle (0.1 micron vs 0.5 micron) and the fewer of them to be tolerated (10 vs 100 vs 1000), the more airflow, the larger the air conditioning load, the higher the energy requirement and the higher the first cost and operating cost of the facility.

Similarly your products’ sensitivity to gases and vapors that may be present in the ventilation air stream should be assessed. Treatment of make-up air with activated carbon filters modified to remove specific gaseous contaminants may be required.

Temperature and humidity are most economically supplied if worker comfort is the driver (68-75ºF and 30-70% RH). Unusually high or low temperature, or humidity specification with tight tolerances (eg. +/-.2ºF), can require high end equipment and controls. This is particularly true if there is a large exhaust air volume, and therefore outside make-up air requirement, that has to be conditioned (and cleaned).

Cleanrooms are typically kept at an air pressure slightly higher than surrounding space to provide a limited amount of exfiltration and thereby prevent leakage of contaminated air into the cleanroom. A pressure on the order of 0.05 inches of water column is appropriate for your “starter” cleanroom. Higher pressures are more expensive, produce higher air noise, and are rarely required. A negative pressure cleanroom, one intended to prevent cleanroom air from leaking outward is possible, but unusual, and the need for such a design should be carefully studied before making an investment.

Other parameters, such as lighting level and quality, sound level, vibration, and air velocity, should be addressed as appropriate for specific nanotech applications.

UPGRADING
When carving out a cleanroom within an existing plant space, it is tempting to maximize the use of existing plant services. Certainly if these services can be adapted to use within the cleanroom, economies can be realized. However some cleanroom specific caveats ought to be observed.

An air conditioning system should be dedicated to the cleanspace. Mixing air from cleanroom and “nonrated” adjacent spaces is not generally recommended. If an existing air conditioning system is available and can be dedicated to the cleanspace, the interior of the supply ducts should be cleaned. A HEPA filter should be installed on the supply side of the air handler. The extra pressure drop associated with this higher efficiency filter may require adjustment of the air handler fan speed or replacement of the fan motor.

Note also that standard comfort air conditioning, when called upon to provide humidity control, particularly dehumidification, may have to be reconfigured (or replaced) to provide such control. Humidification, typically required during cold times of the year, can usually be readily added on to an existing system. Depending on the size and complexity of the cleanroom, and its environmental parameters, it may be most economical to install a new system selected based on process requirements than attempt to modify an existing system.

The air handler of a comfort conditioning system generally provides approximately six air changes per hour (ACH) to the conditioned space. Utilizing this type of system may meet the cooling and heating requirements of the space but once the cleanliness requirement of the space exceeds “controlled environment,” additional HEPA/ULPA filtered airflow will be required. It is common for filtered airflow to increase from dozens of ACH at lower cleanliness classifications to hundreds of ACH in the most stringent cleanrooms. Therefore, the design of the conditioning system and of the filtered air recirculation system are usually best addressed separately. Application of filter fan units offers a neat solution to the requirement for high airflow rates of filtered air (Figure 2).

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SUMMARY
Nanotechnology product research and development eventually calls for a pilot line that permits the production process to be examined, fine tuned, and scaled up as volume increases. Often the facility serves to generate cash as small lots of product are manufactured for introduc tion to the marketplace. The small scale cleanroom facility offers the environment of a full scale production facility, provides the stringent environment commonly required for nanotechnology product manufacture, enables the process to be evaluated in a “real” environment, and offers the opportunity to establish real yields upon which financial projections can be based, all this at a reasonable cost per square foot so important to a start-up operation.

The Bottom Line on Buying a Cleanroom System

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:

• 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 bag-in/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.

• 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

• 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.

What Are Pharmacy Clean Rooms?

Contributor

By Kirsten Acuna
eHow Contributing Writer

A pharmacy clean room is a low-level pollutant environment for the storage and preparation of medication in a hospital setting. Contaminants are constantly produced by facilities, machines and the people in the room. A clean room provides a locale where the air is constantly controlled.

Function

1. Clean rooms hold different colored bins that separate medications, label makers and wash stations. Machinery housed in these rooms contributes in the production of these drugs.

Benefits

2. Clean rooms help ensure the production and manufacturing of medications in a clean safe environment.

Procedures

3. Clean rooms require proper attire that cover workers from head to toe. The standard uniform consists of gloves, face masks and a head cover. Workers must constantly maintain a clean environment in order to keep the room as contaminate-free as possible. The use of high efficiency particulate air filters) helps in maintaining clean air quality. Other filtration devices are also employed to help remove unnecessary particles from the room.

Types

4. Clean rooms are made according to size and the way airflow is circulated through them. People can choose from several types, including all-steel biosafe, hardwall, softwall, double-wall plastic, ventilation, powder-containment and negative-pressure clean rooms.

Interesting Facts

5. Limitations to what can be worn and brought inside a clean room includes rings, keys and cosmetics. Anything that can be considered a contaminate cannot enter the room. This also includes food and drink.

What Are Clean Rooms?

Contributor

By Alden Witt
eHow Contributing Writer

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What Are Clean Rooms?

Clean rooms are, essentially, just what they sound like. They are rooms with a low level of pollutants. These pollutants are not necessarily what is normally considered air pollution, but rather skin particles, dirt, microbes and chemical vapors. A clean room has a controlled amount of all of these.

Classification of Clean Rooms

1. Clean rooms are classified by particles per volume. There are numerous standards of classifying clean rooms. By the FED-STD-209E classifications, a class 10 would have 10 particles larger than .5 micrometers per cubic foot. A class 200 would have 200 such particles.
   By the ISO 14644-1 classifications, a class 3 clean room would have 10^3 particles of .1 micrometers or greater per cubic meter. A class 5 would have 10^5 such particles.
   Ordinary air is generally FED class 1,000,000 or ISO class 9.

Maintaining Clean Rooms

2. Special airflow, filtering, protective clothing and other regulations help maintain a clean room.
   Many common clothing materials are not allowed, particularly those made from natural fibers. Normal pencils and paper are often excluded, partly because they tend to release particles.

Airflow in Clean Rooms

3. The air entering a clean room is filtered to prevent outside contaminants from entering. Staff pass in and out through airlocks, which prevent unclean air from entering with them. Staff members also sometimes are showered with clean air prior to entering.
   Inside the clean room, air is continuously recirculated to remove pollution generated from within (from manufacturing or the staff). Constant airflow from the ceiling is often used to sweep away contaminants, which leave through filters near the floor.
   Clean rooms are sometimes kept at a positive pressures so air leaks will not result in external air entering.

Clean Room Suits

4. In order to prevent particles from staff from contaminating the air, most clean rooms require some sort of protective clothing. This can include boots, gloves, face masks, hats and coveralls. Boots are perhaps the most critical because of contaminants collected by shoe soles. Clean-room shoes have to balance the need for a smooth sole that doesn't track dirt and a safe amount of traction.

Uses of Clean Rooms

5. Clean rooms come in many sizes. Often, entire facilities will be kept as clean rooms for clean manufacturing.
   Clean rooms are often found in the manufacturing of biotechnology, semiconductors and other fields working with sensitive materials.
   Often, manufacturing companies will have semi-clean rooms. While they won't follow all procedures for fully minimized air pollution, they will utilize some of the practices. In general, the lower the cost of the clean room, the lower the standards of cleanliness.