Tuesday, June 28, 2011

Some Traditional and Non-Traditional Cleanroom Uses and Related Contamination Control Practices

Products and processes in many high-tech industries may be severely compromised by airborne particles, dust, chemical vapors, electrostatic discharge, and other contaminants. Industries such as semiconductor manufacturing, pharmaceutical processing, and biotechnology research typically use cleanrooms to control these contaminants as well as temperature and humidity.
ISO 14644, the cleanroom standard series issued by the International Organization for Standardization (ISO), defines a cleanroom as “a room in which the concentration of airborne particles is controlled, and which is constructed and used in a manner to minimize the introduction, generation, and retention of particles inside the room and in which other relevant parameters, e.g. temperature, humidity, and pressure, are controlled as necessary.” This standard provides a method for classifying cleanrooms based on a specified number and size of particles per cubic meter of air. High efficiency particulate air (HEPA) and ultra low particulate air (ULPA) filtration is used to remove airborne contaminants.
Personnel and the activities they perform are a primary source of contamination. The human operator has been characterized as a broad-spectrum particle generator enclosed by inefficient mechanical filters that may also generate and release chemical and biological aerosols to the environment together with potentially destructive electric charges (ESD). To minimize such contamination, cleanroom personnel wear protective apparel such as face masks, gloves, boots, and coveralls, which they put on in a controlled gowning area.
Example Contaminants from Operator
  • Particulate: Skin Flakes, Hair, Eyelashes, Cosmetics, and Tobacco Smoke.
  • Chemical/Organic Matter: Na, Mg, Al, Si, P, S, Cl, K, Ca, Fe - Cosmetics (Bi, Ba, Ti) - Oils - Nasal Effluvia (rich in Na and K) - Oral Effluvia (rich in K and Cl).
  • Biological: Bacteria, Viruses, and Pyrogens.
  • ESD: 20 to 40,000 volts.
Example Contaminants from Street Clothes
  • Particulate: Silica Dust
  • Fibers: Cellulose
  • Chemicals: Varies
  • Biological: Bacteria
Thousands of cleanrooms (controlled environments) around the world host a variety of activities in industries such as the following:
Microelectronics (semiconductor/integrated circuits)
Microcircuits well below the sub-micron level are sensitive to a variety of contaminants, including particles and trace metal impurities (Na, K, Ca, Fe, Ni, Cr, Cu, and Zn). These contaminants cause detrimental device degradation, reliability problems, and manufacturing yield losses. For example a particle as small as 0.5 micrometers can severely impede the coating adhesion on a wafer or chip. To improve yields and lessen production defects, manufacturers put precision instrumentation such as etching and doping devices within a controlled environment such as a cleanroom. In addition to air filtration, the cleanroom must have vibration protection and temperature/humidity control to minimize static electricity.
Food-borne illnesses and microbial contamination, especially pathogenic organisms, are a growing concern worldwide. The major focus of contamination control in the food industry is prevention of cross contamination between ready-to-eat products and raw materials. Food processors are concerned with the spread of bacteria, yeasts, and mold that grow in the moist conditions of processing areas and are carried by air currents throughout the food plant. Meat processing typically takes place in HEPA filtered cleanrooms or “positive pressure” rooms vs. the cold stagnant and contaminated air supplied by refrigeration systems. Cleanrooms allow the use of preservatives to be reduced or eliminated.
Unlike the tightly monitored pharmaceutical industry, in the United States, there is no federal agency responsible for monitoring hospital construction or operation. This function is usually handled at the state level. For example, in California hospital construction comes under the jurisdiction of the Office of Statewide Health Planning and Development (OSHPD). Licensing involves everything from contamination control to emergency procedures, to visitor management.
Tissue Engineering
A branch of biotechnology, this discipline involves growing living tissue, which is very susceptible to contamination. The use of single transit Class M5.5/10,000/ISO-7 cleanrooms with work done in Class M3.5/100/ISO-5 hoods; full multi-level gowning (protocols and apparel) are a must when there is a great concern about non-viable particulate contamination. Viable contamination is certainly also important—genetic engineering (“bacterial farming”).
Per the U.S. Food, Drug, and Cosmetic Act of 1938 as amended (FD&C), cosmetics should not be “adulterated or misbranded” and remain in an uncontaminated condition when used by the consumer (unlike drugs, there is no pre-clearance requirement). Cosmetics are not manufactured in cleanrooms but are tested for microbials in a clean area under aseptic conditions. The industry is self-regulated i.e., testing of raw materials, microbiological controls, air handling, and the many things that go into GMP’s are established voluntarily through industry trade associations.
The application of coatings and paint is subject to two types of contamination: process-related and environmental or human-sourced. Process-related contamination results from the paint, paint distribution system (robotics and spray equipment), airflow, and filtration. The need to control process-related contamination affects facility and booth design, airflow, filtration, humidification, robotics and spray equipment, paint delivery and atomization rates, paint filtration, water systems, and assembly processes. Environmental and human-sourced contaminants, such as personal hygiene products, machine lubricants, packaging materials, and fibers, can account for more than 25% of paint-related defects. Crater-causing contaminants limit paint from adhering to a surface. Particulate contamination under or on a painted surface can produce blemishes ranging from small visual detractors to corrosion-related defects.
The ISO 14644 Series, Cleanrooms and associated controlled environments, is used worldwide to establish the design and operation of cleanrooms. In addition, the Institute of Environmental Sciences and Technology (IEST,has published Standards, Recommended Practices, and Handbooks to assist users in designing, operating, and maintaining cleanrooms and other controlled environments at specification levels.

Modular Softwall Cleanrooms

Simple, Mobile, and Cost Effective
Softwall modular cleanrooms are designed for functionality and reduced cost while providing all the flexible benefits of modular construction. They are tent-like, lightweight, easy-to-assemble structures, which can be installed free standing or suspended from the ceiling of an existing building. Unlike their fixed-wall counterparts, softwall cleanrooms are generally smaller, portable, and can fit into tight spaces. The portable design enables the cleanroom units to be easily moved to another location or disassembled and stored. Because of their relative low cost, softwall cleanrooms are ideal for small or startup businesses, or manufacturers looking for a quick, easy way to expand their cleanroom operations.
The cleanrooms are available in a variety of sizes and classifications, with options to match a customer’s specific needs. From standard 4 feet by 4 feet units, to sizes as large as 24 feet by 36 feet. Larger, custom sizes can be designed and built to meet customer requirements. Because of their modular design, rooms can be expanded or reduced in size without taking the entire cleanroom down, making it easy to add or remove sections. Softwall rooms are also available in a variety of cleanroom classifications, but most commonly in Class 100,000 to Class 10 (ISO 8 to ISO 4) designs.
A wide variety of industries use softwall cleanrooms, from medical device manufacturers to makers of rolled films. This design is also popular in microelectronics and semiconductor manufacturing, as well as electronics repair industries where contaminants cannot be allowed into sensitive areas of electronic devices.
The basic building block of the softwall cleanroom’s modular design is a sectioned ceiling framework made up of tubular steel beams with T-bar cross members. This interlocking ceiling grid system enables easy assembly and cleanroom expansion. The ceiling is supported by tubular steel legs at each of the four corners and reinforced with heavy gauge, triangular steel gussets. Powered HEPA filter units, lighting systems, and ceiling panels are sealed to the grid using gaskets, providing a zero-leak cleanroom.
Image 1
Interior height of the ceiling framework is commonly 8, 9, or 10 feet, although various heights are available depending on the customer application. Standard filter unit height is 14 inches, with a two-inch minimum space required between the filter unit and facility ceiling. The common structure height enables the modular softwall cleanroom to easily fit within an existing building.
Softwall cleanrooms, without a center support, have a maximum size of 12 feet by 12 feet with a leg on each corner. Larger rooms can be constructed, but additional support posts within the structure are required. For example, a room 16 feet by 20 feet would have one center post or a room 20 feet by 32 feet would have three center posts. Other options are available for clear spans without center legs. For example, ceiling-suspended softwall cleanrooms eliminate the need for all support legs and columns. This configuration allows the cleanroom to easily accommodate equipment layout and maximizes floor space utilization.
The walls of most standard softwall modular cleanrooms are made of 20 or 40 mil clear vinyl and are fire retardant with an anti-static additive. Cleanroom-grade softwalls with low outgassing and static-dissipative vinyl are an available option. Entering or exiting most softwall cleanrooms is by way of vinyl strip doorways. The strip door commonly consists of eight-inch-wide, 80 mil thick strips with a two-inch overlap on each side along the length. Entering a cleanroom requires only to push apart the strips, which automatically reseal as they come back together. The strip doors are pre-assembled and are easily mounted to the ceiling structure. Swinging doors in metal frames are an available option when acrylic or Lexan walls are used.
The controlled level of contamination will vary depending on quantity and configuration of filters. For example, the ceiling structure of a Class 10,000 (ISO 7) cleanroom will have a combination of powered HEPA filters, lights, and blank panels. In contrast, Class 10 (ISO 4) cleanrooms require 100% ceiling coverage with powered filters in all ceiling grid sections.
When ceiling space for lighting is limited due to filter requirements, flow-thru lights can be used. These are similar to standard cleanroom lights with the exception that a motorized ceiling HEPA filter unit is mounted directly on top of the light. This fixture is designed with open areas so filtered air is able to flow through the light fixture down into the cleanroom. Flow-thru lights are also valuable in situations where concentrated “clean areas” and lighting need to be achieved within a cleanroom. The filter unit and light fixture are pre-assembled together to form one complete flow-thru light unit.
Filtered air is exhausted from the cleanroom beneath the flexible vinyl walls. An adequate gap of about six-inches between walls and floor is necessary for air to flow through the room and escape. Air volume is typically about 200 feet per minute, and at that rate the flexible walls tend to bow outward a little because of positive air pressure created by the powered filters. A small amount of wall flex is nor mal, but if the wall-to-floor gap is too small, the air will push the panels outward to an unacceptable distance and inhibit good laminar airflow. If the gap is too large, the cleanroom will not keep enough positive pressure to push contaminants out.
Image 2
Like their hardwall counterparts, softwall cleanrooms have a large number of options available depending on customer needs. Anterooms or gowning rooms can easily be added to the cleanroom. They, too, are portable and can be relocated along the outside perimeter of the cleanroom for adaptation or modifications to manufacturing processes.
If needed, softwall cleanrooms can be mobile. When equipped with optional braked casters, they can easily be moved to a different location within a facility or stored. Casters are used for smaller cleanrooms, and customers who wish to install casters on rooms larger than 12 feet by 12 feet should seek advice from their supplier.
Optional acrylic or Lexan panels provide a flexible, yet sturdy and attractive wall alternative. Product passthroughs can also be included in the design. Additional options include: special room heights, solid doors, yellow or opaque sidewalls for ultraviolet light filtration and security, stainless steel frames, building suspension brackets, and ionization equipment.
Modular softwall cleanrooms are pre-fabricated at the factory for quick installation. Customers can easily install standard rooms onsite within one-to-two days. All electrical connections are simplified using a continuous series of plug-together, pre-fabricated wiring system. Starting at the room’s electrical junction box, power cable segments are connected to each ceiling light and powered filter unit. This allows the user to connect any number of lights or filter units within their circuit.
Softwall cleanroom maintenance is simple, but requires regular cleaning to ensure optimum performance. Powered filter units use a prefilter and these must be visually checked on a regular basis. If the filters are dirty, they must be changed. The HEPA filters are somewhat maintenance free, but it is recommended they be re-certified by a third party every year. All interior surfaces and floors must be cleaned on a regular basis.
A modular softwall cleanroom is a low-cost investment, which provides a highly functional cleanroom solution for manufacturers. The flexible structure creates a controlled environment that is able to meet the needs and requirements of small- to large-sized companies. Softwall cleanrooms are designed with the customer in mind, covering a wide range of industries and diverse applications.

Floorplan: 5 simple steps for your next flooring project

New or refurbishment resinous floor and wall system projects can appear overly complex in the early planning stage. Yet, there are key criteria that all manufacturers and their contractors evaluate to arrive at a system recommendation. By understanding and rating the relative importance of these criteria, you can help your resinous system team help you. This article highlights simple steps you can take to optimize your resinous floor and wall system applications.
Step 1: Rank the floor system qualities by how important they are to the project team and assign a weight to them.
Assemble a site team of users of the space that is to be constructed or renovated. Also involve a cross section of facility and maintenance personnel. By allowing each group to voice their concerns and key issues you promote broad buy-in and help ensure you’ve covered all your bases.
Have the team document all important functional and aesthetic requirements you would like the resinous system to have. See Figure 1 for a list of key criteria.
Additional criteria might include:
  • Cleanability
  • Slope to Drain
  • Repairability/Maintenance
  • Impact on Project Schedule
  • LEED Impact
  • Budget
  • Detailing corners, coves, etc.
  • Aesthetics of the System (gloss/low sheen; solid color; terrazzo; decorative flake; decorative quartz)
Once your list is complete, have each team member rank every system attribute on a scale of 1 to 10. Total each and rewrite your list in order of importance to the team. This might take a few repetitions but in the end you will have consensus.
Next, clearly establish how many square feet of resinous floor and wall finishes are going to be installed. For refurbishment projects, develop a realistic plan for how much space (how many square feet) you can allocate to the resinous contractor without interruption. Keep in mind access to critical corridors and spaces. This will help the contractor understand how many mobilizations will be required to complete your project.
Other relevant information you can supply includes: strong likes/dislikes with previous resinous systems at your site, how long you want the system to last, accessibility for the crew (how long does it take to get into the space and what is required), noise/vibration limitations, other work being performed concurrently both in the facility and as part of the construction process, and a venting plan.
Figure 1
Step 2: Establish a Budget
Take the results of Step 1 and schedule a meeting with your design team including the architect, resinous system supplier, and installer. At this point, the design team can provide samples and price ranges for options which meet your site team’s criteria. For example, an 1/8" thick double broadcast epoxy colored quartz system might be installed for $6.00 - $8.00 per square foot. An 1/8" thick methyl methacrylate flake floor might be installed for $15.00 - $18.00 per square foot.
The most basic impact on budget comes from how many square feet the contractor can address each day and the number of days required installing the system. For example, if the contractor is given a small space to work on with a system that requires a large number of steps, your installed cost per square foot will be high. Conversely, given the same set of circumstances, a large number of square feet with few installation steps will result in a low installed cost per square foot.
Step 3: Keep It Simple!
Your design team will most likely provide you with more than one resinous floor and wall system option that meets your site criteria. Don’t be afraid to ask the team why they are recommending a particular system or the downside to utilizing a less expensive option. Don’t be tempted to over-engineer your resinous flooring system. An excellent example of this relates to how you build thickness beneath the resinous flooring system. Added thickness could be necessitated by a need for slope-to-drain or to restore flatness after aggressive surface preparation. Rather than building thickness out of the resinous floor system resin, many manufacturers offer fast-setting, high strength cementitious mortar systems which can be half to a third of the cost of utilizing the flooring system resin. Just make sure these materials are produced and packaged by the flooring manufacturer and meet the strength requirements of the project.
Step 4: Look Ahead
Don’t make your resinous floor and wall system decision in a time vacuum. Think about long-term maintenance implications. In Figure 1, one of the selection criteria listed is ultraviolet (UV) resistance. The reason it is important is because many of the systems offered today discolor with exposure to light. UV resistance is a relevant consideration because if noncolorfast materials are selected, they will discolor as they age. A large percentage of resinous floor and wall systems are re-coated or completely redone because they have lost their aesthetics rather than lost their basic performance properties. If you think about what the system is going to look like five to seven years from now instead of what the shiny new sample looks like today, it may drive you and the site team toward color-stable technologies.
Another consideration for the future is how do you patch and repair the systems? There is no system that can’t be damaged over time. How disruptive and how involved are simple repairs and patches? What will they look like? Does the system have a strong odor? Can it be repaired while the facility is in operation or will it necessitate a shutdown of the entire cleanroom? Ask the design team these questions as well as cleaning recommendations and required equipment. Find out how long it takes for the materials to cure before normal operations can proceed.
Simply doing quarterly inspections and taking care of gouges, impact damage, etc. can save you a lot of money. This helps avoid always being in an emergency repair situation necessitated by having to patch damaged areas that started small but became large due to lack of attention. Ask the resinous system supplier and contractor if they will include an annual inspection in their quotation and who would be responsible for these inspections. See if there is a cost associated with these inspections. Also, set up a contact and speed of response procedure to report damage as it occurs.
Step 5: Check Out your Supplier/Contractor Team
Assuming a proper system is selected, the final step involves making sure you have the right supplier/contractor team lined up—before a contract is let. Most resinous floor and wall system architectural guide specifications call for certain submittal information. These items should be evaluated whether you are handling the resinous system contract directly or the project is being let as a subcontract by a general contractor or construction manager. Let’s take a close look at them one by one.
  1. Industry Experience: Is the contractor and manufacturer familiar with typical cleanroom conditions? Ask for a list of previous projects.
  2. Project Experience: Has the manufacturer/contractor team dealt with projects of similar size and complexity to yours? Ask for references.
  3. Stability: How long has your contractor/supplier been in business? Ask for their annual volume and an annual report. If problems develop during an installation, they can be very expensive to fix, making financial strength and stability an extremely important piece to investigate.
  4. Workforce: Make sure the installer’s team has experience with cleanrooms. Ask for the names of key personnel that are going to be on your project and make sure they are company employees.
  5. Safety: Ask for documentation of the installer’s safety program, certificate of insurance, and incident rate.


Any successful project starts with a clear identification of needs. Establish key resinous system attributes and understand what is most important to your site team. Enlist a design team consisting of your architect, resinous flooring supplier, and contractor to establish your budget taking into account near-term and long term requirements. Finally, before you award your contract, perform a detailed check on your supplier/resinous system team to make sure they meet your needs. Following these simple steps will greatly enhance the probability of a successful resinous floor and wall system project.

Point of View - The Importance of Ongoing Facility Monitoring