A Basic Introduction to Clean Rooms

A Basic Introduction to Clean Rooms

By Roger McFadden
Senior Scientist, Staples Inc.

                  A cleanroom is a controlled environment where products are manufactured. It is a room in which the concentration of airborne particles is controlled to specified limits. Eliminating sub-micron airborne contamination is really a process of control. These contaminants are generated by people, process, facilities and equipment. They must be continually removed from the air. The level to which these particles need to be removed depends upon the standards required. The most frequently used standard is the Federal Standard 209E. The 209E is a document that establishes standard classes of air cleanliness for airborne particulate levels in cleanrooms and clean zones. Strict rules and procedures are followed to prevent contamination of the product.

            The only way to control contamination is to control the total environment. Air flow rates and direction, pressurization, temperature, humidity and specialized filtration all need to be tightly controlled. And the sources of these particles need to controlled or eliminated whenever possible. There is more to a clean room than air filters. Cleanrooms are planned and manufactured using strict protocol and methods. They are frequently found in electronics, pharmaceutical, biopharmaceutical, medical device industries and other critical manufacturing environments.

            It only takes a quick monitor of the air in a cleanroom compared to a typical office building to see the difference. Typical office building air contains from 500,000 to 1,000,000 particles (0.5 microns or larger) per cubic foot of air. A Class 100 cleanroom is designed to never allow more than 100 particles (0.5 microns or larger) per cubic foot of air. Class 1000 and Class 10,000 cleanrooms are designed to limit particles to 1000 and 10,000 respectively. 

             A human hair is about 75-100 microns in diameter. A particle 200 times smaller (0.5 micron) than the human hair can cause major disaster in a cleanroom. Contamination can lead to expensive downtime and increased production costs. In fact, the billion dollar NASA Hubble Space Telescope was damaged and did not perform as designed because of a particle smaller than 0.5 microns.

            Once a cleanroom is built it must be maintained and cleaned to the same high standards. This handbook has been prepared to give professional cleaning staff  information about how to clean the cleanroom.

 What is Contamination?

            Contamination is a process or act that causes materials or surfaces to be soiled with contaminating substances. There are two broad categories of surface contaminants: film type and particulates. These contaminants can produce a “killer defect” in a miniature circuit.  Film contaminants of only 10 nm (nanometers) can drastically reduce coating adhesion on a wafer or chip. It is widely accepted that particles of 0.5 microns or larger are the target. However, some industries are now targeting smaller particles.

            A partial list of contaminants is found below. Any of these can be the source for killing a circuit. Preventing these contaminants from entering the cleanroom environment is the objective. It requires a commitment by everyone entering the cleanroom to make it happen. Professional cleaning personnel need to be aware of the importance of controlling contaminants. Strict procedures should be followed whenever entering or cleaning a cleanroom. Compromise is not acceptable when cleaning in a cleanroom.

Sources of Contamination

            This is a partial list of some of the commonly known contaminants that can cause problems in some cleanroom environments. It has been found that many of these contaminants are generated from five basic sources. The facilities, people, tools, fluids and the product being manufactured can all contribute to contamination. Review this list to gain a better understanding of where contamination originates.

1.     Facilities

Walls, floors and ceilings

Paint and coatings

Construction material (sheet rock, saw dust etc.)

Air conditioning debris

Room air and vapors

Spills and leaks

2.    People

Skin flakes and oil

Cosmetics and perfume

Spittle

Clothing debris (lint, fibers etc.)

Hair

 3.   Tool Generated

Friction and wear particles

Lubricants and emissions

Vibrations

Brooms, mops and dusters

4.    Fluids

Particulates floating in air

Bacteria, organics and moisture

Floor finishes or coatings

Cleaning chemicals

Plasticizers (outgasses)

Deionized water

5.    Product generated

Silicon chips

Quartz flakes

Cleanroom debris

Aluminum particles

Key Elements of Contamination Control

              We will look at several areas of concern to get a better idea of the overall picture of contamination control. These are the things that need to be considered when providing an effective contamination control program.

HEPA (High Efficiency Particulate Air Filter) - These filters are extremely important for maintaining contamination control. They filter particles as small as 0.3 microns with a 99.97% minimum particle-collective efficiency.  

CLEANROOM ARCHITECTURE - Cleanrooms are designed to achieve and maintain a airflow in which essentially the entire body of air within a confined area moves with uniform velocity along parellel flow lines. This air flow is called laminar flow. The more restriction of air flow the more turbulence. Turbulence can cause particle movement.

FILTRATION - In addition to the HEPA filters commonly used in cleanrooms, there are a number of other filtration mechanisms used to remove particles from gases and liquids. These filters are essential for providing effective contamination control.

CLEANING - Cleaning is an essential element of contamination control. Decisions need to made about the details of cleanroom maintenance and cleaning. Applications and procedures need to be written and agreed upon by cleanroom management and contractors (if used). There are many problems associated with cleaning. Managers need to answer the following questions before proceeding with any cleanroom cleaning program:

1.    What is clean?

2.    How is clean measured?

3.    What cleaning materials can be used in the cleanroom?

4.    When can the cleanroom be cleaned?

5.    How frequent does it need to be cleaned?

CLEANROOM GARMENTS - The requirements for cleanroom garments will vary from location to location. It is important to know the local garment requirements of the cleanroom management. Gloves, face masks and head covers are standard in nearly every cleanroom environment. Smocks are being used more and more. Jump suits are required in very clean environments.

HUMANS IN CLEANROOMS - There are both physical and psychological concerns when humans are present in cleanrooms. Physical behavior like fast motion and horseplay can increase contamination. Psychological concerns like room temperature, humidity, claustrophobia, odors and workplace attitude are important. Below are several ways people produce contamination:

1.    Body Regenerative Processes-- Skin flakes, oils, perspiration and hair.

2.    Behavior-- Rate of movement, sneezing and coughing.

3.    Attitude-- Work habits and communciation between workers.

              People are a major source of contamination in the cleanroom. Look at the people activies listed below. Notice the number of particles produced per minute during these activities.

PEOPLE ACTIVITYPARTICLES/MINUTE (0.3 microns and larger)

Motionless (Standing or Seated)100,000

Walking about 2 mph5,000,000

Walking about 3.5 mph7,000,000

Walking about 5 mph10,000,000

Horseplay100,000,000

                                                                    

COMMODITIES - Care is taken when selecting and using commodity items in cleanrooms. Wipers, cleanroom paper and pencils and other supplies that service the cleanroom should be carefully screened and selected. Review of the local cleanroom requirements for approving and taking these items into the cleanroom are essential. In fact, many cleanroom managers will have approval lists of these types of items.

COSMETICS - Many cosmetics contain sodium, magnesium, silicon, calcium, potassium or iron. These chemicals can create damaging particles. Cleanroom managers may ban or restrict cosmetics in the cleanroom. This is usually dependent upon the threat to the product being made in the cleanroom. A recent mirror on a space telescope was fogged up from the cologne that was present in the cleanroom.

MEASUREMENT AND INSTRUMENTATION  - Some important measurements related to contamination control are particle count, air flow & velocity, humidity, temperature and surface cleanliness. Cleanroom managers usually have specific standards and/or instruments to measure these factors.

ELECTROSTATIC DISCHARGE (ESD) - When two surfaces rub together an electrical charge can be created. Moving air creates a charge. People touching surfaces or walking across the floor can create a triboelectric charge.  Special care is taken to use ESD protective materials to prevent damage from ESD. Cleaning managers should work with their personnel to understand where these conditions may be present and how to prevent them.

Cleaning Procedures for Clean Rooms

 What follows are some recommended procedures for cleaning cleanrooms. It is important to emphasize that these procedures are guidelines and not standards or rules. The procedures listed here are routine cleaning tasks. Local cleanroom cleaning procedures may supercede the ones listed here. It is important for cleaning managers to review all cleaning procedures to be used in a cleanroom with the cleanroom management. A detailed cleaning schedule should be prepared for every cleanroom. Here are some procedures to be completed when cleaning a Class 10,000 cleanroom:

Cleaning Procedures for a Class 10,000 Cleanroom

Housekeeping maintenance of the cleanroom and restricted areas is essential to assure quality. Cleaning of a cleanroom should be performed on a daily basis. Improper cleaning of the cleanroom can lead to contamination and a loss in end user product quality. Proper selection of equipment and materials is important for proper cleaning. Only products that have proven cleanroom performance records should be considered for use in cleanrooms. These products should be listed and all vendors should be informed about the strict policies of how products are qualified. All procedures should be strictly enforced. Below are some examples of how to organize the cleaning to be done in a cleanroom. These are NOT schedules or exact procedures. They are guidelines for preparing work procedures and schedules. Local requirements must be included in any cleaning program.

List of Some of Equipment and Supplies Needed to Clean the Cleanroom

(All supplies must meet the Class 10,000 minimum requirements)

                                    1.             Cleaning and disinfecting solutions

                                    2.             Cleanroom mops

                                    3.             Cleanroom vacuum cleaner (if allowed)

                                    4.             Cleanroom wipers

                                    5.             Cleanroom mop bucket and wringer

List of Cleaning Tasks to be Completed in the Cleanroom

(Frequency may vary depending upon local requirements) 

                                    1.             Cleaning of all work surfaces in the controlled environment.

                                    2.             Vacuuming (if allowed) of the floors and work surfaces.

                                    3.             Emptying of appropriate trash and waste.

                                    4.             Cleaning of the doors, door frames and lockers in the pre-staging                                     area and gowning areas using the approved cleaning solution.

                                    5.             Mop gowning and cleanroom floors.

Cleaning Procedures for a Class 1000 Cleanroom

Below is a sample of a cleaning program in a Class 1000 Cleanroom. This is only a sample of a program. Local standards and requirements must be followed.

AreaDescription of WorkFrequency

101Change tacky matsEvery 2 hours

102Wet mop with approved mop, cleaner & DI water2 times per shift

103Dust mop (if allowed)2 times per shift

104Remove trash, sweep, mop with appropriate cleaner wipe down tables and coffee area, clean walls and recycle cans1 time per shift

105Vacuum entry mats, sweep and mop floors1 time per shift

106Mop floor with pre-burnish cleaner and tap water1 time per shift

107

Remove trash. Always wear gloves. Never take waste containers inside cleanrooms.

1 time per shift

108Wet mop floors1 time per shift

109Remove acid and solvent trash1 time per shift

110Clean and replenish dispenser in all restrooms3 times per week

111Vacuum floor (if allowed)2 times per week

112

Clean stainless steel pass throughs with s/s cleaner and appropriate wipes

1 time per week

The list above is a sample of some of the common tasks that need to be performed in a Class 1000 cleanroom. The list is not exhaustive. But gives some ideas of how to prepare work schedules and procedures. An assessment of the cleanroom in conjunction with cleanroom management will help define these tasks and frequencies.

Cleaning Procedures for a Class 100 Cleanroom

ZoneProcedureFrequency

Zone 1aTrash removalOnce daily

 Mop walkwaysOnce a week

 Wipe down horizontal surfacesOnce monthly

Zone 1bPull tacky matsEvery 2 hours

Zone 1cMop and trash removalOnce daily

 Wipe down walls and trimOnce a week

Zone 1dMop and trash removalOnce daily

 Wipe walls and trimOnce a week

Zone 2aMop  Twice a shift

 Wipe walls and trimOnce a week

 VacuumOnce monthly

Zone 2bMop and trash removalOnce per shift

Zone 2cWipe down walls, windows, doors, trim, showers, passthroughs and fire extinguishers.Once a week

The list above is a sample of some of the common tasks that need to be performed in a Class 100 cleanroom. The list is not exhaustive. But gives some ideas of how to prepare work schedules and procedures. An assessment of the cleanroom in conjunction with cleanroom management will help define these tasks and frequencies.

General Cleanroom Regulations

Below is a list of general regulations recommended as a minimum for the successful operation of a cleanroom. All professional cleaning personnel should be aware and follow these regulations at all times.

1.    All personal items such as keys, watches, rings, matches, lighters and cigarettes should be stored in the personal locker outside the gowning room.

2.    Valuable personal Items such as wallets may be permitted in the cleanroom provided they are NEVER removed from beneath the cleanroom garments.

3.    NO eating, smoking or gum chewing allowed inside the cleanroom.

4.    Only garments approved for the cleanroom should be worn when entering.

5.    NO cosmetics shall be worn in the cleanrooms. This includes: rouge, lipstick, eye shadow, eyebrow pencil, mascara, eye liner, false eye lashes, fingernail polish, hair spray, mousse, or the heavy use of aerosols, after shaves and perfumes.

6.    Only approved cleanroom paper shall be allowed in the cleanroom.

7.    Approved ball point pens shall be the only writing tool used.

8.     Use of paper or fabric towels are prohibited. Use of hand dryers equipped with HEPA filters are suggested.

9.    Gloves or finger cots should not be allowed to touch any item or surface that has not been thoroughly cleaned.

10.    Only approved gloves, finger cots (powder-free), pliers, tweezers should be used to
handle product. Finger prints can be a major source of contamination on some products.

11.    Solvent contact with the bare skin should be avoided. They can remove skin oils and increase skin flaking.

12.    Approved skin lotions or lanolin based soaps are sometimes allowed. These can reduce skin flaking.

13.    All tools, containers and fixtures used in the cleaning process should be cleaned to the same degree as the cleanroom surfaces. All of these items are a source of contamination.

14.    NO tool should be allowed to rest on the surface of a bench or table. It should be place on a cleanroom wiper.

15.    Only cleanroom approved wipers are allowed to be used. The wipers must be approved for the Class of cleanroom being cleaned.

16.    ALL equipment, materials and containers introduced into a sterile facility must be subjected to stringent sterilization prior to entrance.

17.    NO ONE who is physically ill, especially with respiratory or stomach disorders, may enter a sterile room. This is a good practice in any cleanroom environment.

 Personal Actions Typically Prohibited in Cleanrooms

1.   Fast motions such as running, walking fast or horseplay.

2.   Sitting or leaning on equipment or work surfaces.

3.   Writing on equipment or garments.

4.   Removal of items from beneath the cleanroom garments.

5.    Wearing the cleanroom garment outside the cleanroom.

6.    Wearing torn or soiled garments.

 

Source: http://www.coastwidelabs.com/Technical%20Articles/Cleaning%20the%20Cleanroom.htm

Understanding Cleanroom Apparel Sterilization

How are cleanroom garments validated as sterile for use in an aseptic cleanroom?

Sterilization is a process that is intended to destroy viable forms of microbial life including bacteria, molds, yeasts, viruses, protozoa, and algae (including bacterial spores) to an acceptable sterility assurance level (SAL). SALs were first used in the food canning industry and refer to the degree to which an item is expected to be non-sterile after exposure to a sterilization process. While we use phrases like “terminal sterilization,” we must remember that sterilization is a matter of degree or probability. In a sterilization process, the nature of microbiological death is therefore described by an exponential function, an expression of probability. For instance, a SAL of 10-6means that there is a one in a million chance (probability) that a microorganism will remain after the sterilization process. However, while this probability can be reduced to a very low number, it can never be reduced to zero. ANSI/AAMI ST67:2003 contains a decision tree to be used to determine the SAL for medicaldevices to be terminally sterilized.

Sterilization is necessary when microorganisms are a contaminant. Such cases would include surgery, the implantation of medical devices, or the injection of solutions into the body. Sometimes, the device, instrument, or solution can be sterilized and packaged until it is ready for use. Often, however, sterilization, regardless of method, has a deleterious effect on the product. In such cases, the alternative is asepsis, the prevention of contact with microorganisms. Aseptic processing or manufacturing generally requires the use of a cleanroom and cleanroom apparel. A sterile cleanroom is often called a sterile suite or aseptic cleanroom. These rooms are meticulously maintained in a sterile condition by rigorous housekeeping and special decontamination procedures governed by the FDA and detailed in the Federal Guidelines to Good Manufacturing Practice (GMP). Note: If you see cGMP, the small case “c” stands for “current.”

Cleanroom garments used in aseptic cleanrooms must be sterile. ANSI/AAMI ST67:2003 identifies the sterility assurance levels for terminally sterilized products. Many companies manufacturing products in an aseptic clean-room require all components used in aseptic processing, including cleanroom garments, to be terminally sterilized to 10-6SAL.

There are three typical methods of sterilizing clean-room garments: steam autoclaving, ethylene oxide (EtO), and ionizing radiation (gamma or electron beam). While each has advantages and disadvantages, gamma irradiation is the most popular method used today.

STEAM AUTOCLAVING
Steam autoclaving is the process of attaining sterility by means of saturated steam and pressure. Usually, the object to be sterilized is wrapped in a vapor-permeable (Tyvek™ paper or cloth) bag and subjected to a high temperature and pressure (121 °C at 15 psi for 15 minutes is common). Unlike dry heat sterilization, steam is much more efficient in penetrating and carrying heat to every surface of the object being sterilized. Steam auto-claving is reasonably convenient, fairly efficient, and widely used for general sterilization of materials that aren’t heat, pressure, or moisture sensitive. Surgical instruments and bed linens are examples of materials that are autoclave compatible. Many injectible solutions and plastic implantable devices are examples of materials that would boil away, cook, or melt if subjected to autoclave sterilization. Historically, steam autoclaving was the primary method of sterilizing cleanroom garments. This was something that the customer did on site. There are quite a number of disadvantages associated with this method, however. For instance, auto-claving causes most cleanroom garments to shrink, often up to two full sizes. This is especially true of the older (and now nearly obsolete) taffeta and herringbone garments. Shrinking, aside from the obvious fit problems this would cause, causes puckering and deformation around zippers and seams sufficient to allow viable and non-viable particle excursions. Steam autoclaving also tends to set in wrinkles, making the garment very unsightly, degrade the fabric prematurely, and affect filtration characteristics. It should be noted that there are some cases yet today where autoclaving can hardly be avoided. This is when the garments must be sterilized before being returned to the garment service provider.

EtO
EtO is a sterilization method that saw wide use for many years, especially for sterilizing cleanroom garments. EtO is a gas that kills microorganisms. In use, the wrapped objects to be sterilized are placed in a vacuum chamber where the air is slowly evacuated and replaced with EtO. Later, this gas is evacuated and replaced with air. Unfortunately, the EtO is very dangerous to humans so the product has to undergo an outgassing/quarantine period of up to 14 days while spore strips are incubated and the residual EtO drops to a safe level. EtO is hardly used at all today to sterilize cleanroom apparel. It is not considered safe or state-of-the-art and requires at least one additional week’s supply of garments to accommodate the extended apparel service cycle. Apparel service companies using EtO cannot compete with those that use other sterilization methods that do not require the extended quarantineperiod.

IONIZING RADIATION
High-energy ionizing radiation is the preferred method for sterilizing cleanroom apparel today. It takes two forms: gamma irradiation and electron beam (e-beam) radiation. Since the latter is not being successfully used to sterilize cleanroom garments because of penetration and load density problems, I will discuss only gamma irradiation. Gamma rays are produced by the decay of cobalt 60, a radioactive isotope of cobalt. Gamma rays are electromagnetic radiation of great penetrating power, emitted by the nucleus of the radioactive atom during decay; they are somewhat similar to an x-ray but shorter in wavelength. In use, garments are cleanroom laundered, packaged, and exposed to gamma irradiation at a contract sterilizer. Here, the garments are exposed to gamma rays in a controlled manor until the minimum specified dose has been administered. There are two kinds of contract gamma facilities, continuous and batch. Before garments can be gamma irradiated, however, validation protocol has to be followed to determine the correct dosage, formerly measured in rads and now measured in “grays.” The validation protocol is specified in the AAMI/ANSI/ISO 11137-1-2006 document entitled “Sterilization of health care products – Radiation – Part 1: Requirements for development, validation and routine control of a sterilization process for medical devices.” It is important to accurately determine the dosage required to obtain the desired sterility assurance level for two reasons. First, gamma irradiation is destructive so the minimum specified dose should be as low as practical with the maximum specified dose being as low as practical too. While it is generally known and accepted, for instance, that 25 kilograys (2.5 megarads) are more than sufficient, it is not a good idea to simply specify 25 kilograys without doing the required validation. A good cleaning/disinfecting process might produce a low bioburden (the number and types of viable microorganisms with which an item is contaminated) and permit irradiation at a lower dose, thus extending garment life while still affording the specified SAL. The second reason for accurately determining the gamma dose appropriate to the specified SAL is liability. Someone’s life could be at risk if the dose has not been set properly, or if the process drifts out of control. It is because of the high liability aspect and the constant pressure felt by our customers from the FDA that the cleanroom garment service providers must undergo such rigorous customer audits. This is serious business and the cleanroom garment service providers must be accountable for their claims.

The gamma irradiation sterilization validation protocol starts with determining the bioburden on the sample item proportion (SIP). The SIP is 10% of the product so a process monitor is used that represents a 10% clean-room coverall. This is called a device. Three lots of 10 devices are washed with other contaminated garments, dried with other garments, and packaged. These are sent to an off-site laboratory to undergo an exhaustive extraction for bioburden. The filter used during the extraction is incubated and the aerobic bacteria, mold, and yeast colony forming units (CFUs) are counted for each of the thirty samples and an average is obtained. This number is then multiplied by 10 to determine the number of CFU per device (coverall). A chart in the “ANSI/AAMI/ ISO 11137-2-2006 Sterilization of health care products – Radiation – Establishing the sterilization dose” then indicates a dosage that should produce a biological reduction of ten to the minus two or fewer than two positive devices per hundred samples. A corresponding dose is shown that statistically presumes a higher SAL (if the lower SAL is achieved). This lower number is known as the verification dose and requires that one hundred additional samples be prepared as before and then sent to the contract sterilizer with an instruction to irradiate at the lower verification dose. The samples are then extracted and incubated. If there are two or fewer positive samples per the one hundred sample lot, then it can be statistically presumed that the higher dose on the table will produce its respective SAL — assuming that the process stays in control and no specifics of the process change. A change in the process requires a complete re-validation. Additionally, at the time of validation, a one-time analysis for bacteriostasis/fungistasis and exhaustive bioburden is performed.

The calculated sterilization dose becomes one component of the customer specifications for gamma irradiation of the product. Other factors are the density of the product, the dimensions, and the weight of the product in the transport container used. The contract sterilizer performs a dose mapping of each product. This assures that the correct radiation dose is delivered to the product every time. Dosimeters are placed on the product during the gamma irradiation process. After irradiation, the dosimeters are removed and read using a calibrated spec-trophotometer. The product is released by Quality Assurance based on the dosimetry readings’ compliance with the customer’s specified minimum and maximum gamma dose for the product.

It is incumbent for the supplier of either reusable or disposable clean-room garments to validate its sterile garment program for gamma radiation per ANSI/AAMI/ISO 11137-1-2006, “Sterilization of Health Care Products - Radiation – Part 1: Requirements for Development, Validation and Routine Control of a Sterilization process for medical devices” and ANSI/AAMI/ISO 11137-2-2006, “Sterilization of health care products – Radiation – Part 2: Establishing the Sterilization Dose” to assure its promise to deliver garments sterilized to the contracted SAL by performing dose audits every three months. The device bioburden analysis is performed per ANSI/ AAMI/ISO 11737-1, “Sterilization of medical devices – Microbiological methods – Part 1: Determination of the population of microorganisms on product.” The AAMI sterility analysis is performed per ANSI/ AAMI/ISO 11737-2, “Sterilization of medical devices – Microbiological methods – Part 2: Test of sterility performed in the validation of a sterilization process.” Section 12.1.3.1 in ANSI/AAMI/ISO 11137-1-2006, “Frequency of sterilization dose audits,” states that the frequency of dose audits may be reduced to every six months if there has not been a change in the validated system and all quarterly dose audits have passed in the previous year. If there is a failure, dose audits must be performed every three months. Even if there has not been a change in the validated system, dose audits must be performed at least once a year.

Source: http://www.cemag.us/articles/2007/05/understanding-cleanroom-apparel-sterilization-part-1

Reusable Cleanroom Garments

In the December issue of CleanRooms, this column focused on the use of disposable garments. This month, the alternative-garments that are periodically laundered and reused-is explored. Reusable cleanroom garments have the potential for comfort and durability, and may reduce the cost per use while reducing waste. Reusable products can provide high-performance protection; however, cleanroom garments will deteriorate over time due to wear and the processing cycles of washing, drying and sterilization.

All garment systems must be worn correctly to be effective. There are many designs, providers and reprocessors available to meet the needs of varied cleanroom applications. One of the pharmaceutical industry’s main concerns in a cleanroom garment is sterility to decrease the bioburden in the cleanroom. Semiconductor manufacturers, on the other hand, are not concerned with sterility, but rather with particulate control. Because of these differences in requirements, the two industries have different preferences and needs with respect to cleanroom reusable garments.

Curt White of Aegis Environments (Midland, Mich.; www.microbeshield.com) notes, “Cleanroom reusable garments have evolved into unique and innovative systems utilizing design, fabric compositions, composites and finishes to meet the increasing demands for protection and comfort required by the ever-expanding end uses of cleanroom garments. These added functional needs are an outgrowth of a market trend that [regards] the cleanroom garment as an active component of a larger cleanroom environmental-control program.”

White continues, “Cleanroom garments have gone far beyond the historical function of preventing particle exposure, reaching into style and function. Comfort and increasing demand for more and more functional properties are higher on the needs list than in the past. Cleanroom garments must not release particles or fibers into the environment, yet must provide for the comfort of the wearer. They must also provide for the productivity and quality at the specific work site, for work processes, and for the products being produced. This challenge is being laid out as geometries for cleanroom processes decrease, nanoparticles become more common, and the manufacturing of personal electronics continues to explode. Concern over pandemics and foodborne illnesses is increasing the use of cleanroom garment systems for the protection of workers as well as for contamination control of products and environments.”

Particulate contamination

Reusable garments capture and entrain particles to prevent them from escaping into the cleanroom environment. Cleanroom personnel can contribute about 25 percent of the airborne particulate contamination in the cleanroom, according to Robin Howie of Robin Howie Associates (Edinburgh, Scotland). Of the millions of particle shed by the cleanroom worker, viable particles include bacteria, molds and yeast, and nonviable particles can include hair, dead skin cells and dandruff. Elements such as sodium, potassium, chloride and magnesium may also come from the human body. Loose fabric particles from clothing can also contribute to contamination. The higher the class of cleanroom, the greater the need for contamination control, ultimately leading to a full-body contamination-control suit.

Sterility

Sterile environments require garments with fabrics that can withstand multiple processing and sterilization cycles. According to Jan Eudy of Cintas Cleanroom Resources (Mason, Ohio; www.cintascleanroom.com), “Cleanroom garments may be sterilized by electron beam (E-beam) sterilization, ethylene oxide (ETO) sterilization, gamma sterilization, or steam sterilization (autoclaving). Currently, gamma sterilization is the most cost-effective method of sterilization for cleanroom materials. However, for reusable cleanroom garments utilizing polytetrafluorethylene (PTFE) membranes, gamma sterilization and ETO sterilization are not an option because they degrade the polymer. Cleanroom apparel used in the U.K. and Europe may be steam-sterilized. Steam sterilization of cleanroom apparel can cause shrinkage and wrinkling of the reusable garment system. Additionally, there are cleanroom-compatible components that are not compatible with steam sterilization. Sterility validation of steam sterilization is performed per ANSI/AAMI/ISO 11134: 1993 for industrial facilities or ISO 13683:1997 for healthcare facilities. With gamma sterilization, the cleanroom garment launderer validates the gamma dose and provides documented evidence of the sterility assurance level (SAL). Audits of the contract sterilizer are also performed. All cleanroom materials used in sterile cleanroom manufacturing must undergo a quarterly dose-audit test and be validated for sterility assurance levels. Cintas, for example, has validated its sterile reusable garments to 10-6 SAL.”

In sterile environments, Richard Bryant of Nitritex (Suffolk, U.K.; www.nitritex.com) states that it’s recommended that cleanroom undergarments be used as an alternative to street clothes. These should be manufactured using nonlinting polyester barrier fabrics. The use of nonlinting polyester undergarments with a good coverall containment system will lower the number of particles carried into the cleanroom environment. Because particles are the main mode of transportation for microbes, a containment system should also lower the number of microbes carried into the controlled environment. The most comfortable choice will be a fabric with excellent wicking properties to allow rapid dispersion of perspiration.

John Smith of Precision Fabrics Group (Greensboro, N.C.; www.precisionfabrics.com) explains that, for pharmaceutical applications, “It has been shown that the number of bacterial colony-forming units is reduced using an antimicrobial. By doing so, the bioburden is reduced going into the laundering and sterilization steps. Even in less critical clean environments, the use of a nonmigrating antimicrobial can inhibit the growth of mildew and mold that can create odor over time. It is very important that the antimicrobial used not allow the mutation of bacteria to occur. The last thing we need is to inadvertently create a worse problem.”

Static control

The electronics and semiconductor industries do not focus on sterility, but rather on particulate and static control. Some processes require the garments to be static dissipative, containing electrostatic discharge properties (ESD).

Michele McSwain of TW CLEAN (Carlsbad, Calif.; www.twclean.com) remarks, “As electronic components continue to decrease in size, and as airborne, charged particles become a higher concern in cleanroom control, the attention to generation and management of electrostatics is increasing.”

The Electrostatic Discharge Association (www.esda.org), a primary training and investigation body in the development of standards and test methods for the industry on the subject of electrostatics, has recently published a technology road map, free for download on the Web site, highlighting the expected intolerance to static electricity based on input from major U.S. corporations. With the road map in mind, the ESDA has developed S20.201, a standard covering the essentials for developing a static-control program. Garments are a part of the total control program and are tested to STM2.1-1997 “for the Protection of Electrostatic-Discharge-Susceptible Items” (which is currently being updated).

Cleanroom garments made of clean, non-sloughing but insulative polyester fabric generate static charges whenever a wearer moves. The addition of carbon threads to the fabric provides a path for charges to migrate. A continuous path to ground at the garment level ensures that these free-floating charges are directed immediately to the ground and guarantees their elimination.

ESD garments should have a low propensity for triboelectric charging and a low resistance to fast dissipation in order to avoid charge accumulation. Microelectronic components can be damaged by static discharge. Also, microorganisms are known to develop on particles adhering to garments that have a static charge. This is unacceptable in pharmaceutical environments. It is therefore essential that the fabric utilized allow the garment to continually dissipate any static buildup.

Cleanroom garments are typically made from synthetic materials, which include nylon, polyester, polytetrafluoroethylene, polyvinylchloride and butyl or nitrile rubbers. These materials are electrically-insulating materials known as dielectrics, which can become electrostatically charged by friction.

Static dissipative fabrics typically incorporate a conductive carbon filament, which is less than 1 percent by weight of the finished material. The high-quality carbon fiber must be used and remain effective throughout the life of the garment and the washing cycles to ensure that the static dissipative qualities remain effective. The carbon fiber is woven into the fabric in either a grid or stripe format, providing a path for charges to migrate.

According to Jan Eudy, “ESD testing of cleanroom garments is based on application standards and is not cleanroom-specific. The Institute of Environmental Sciences and Technology (IEST) has a committee working to create ESD cleanroom-specific garment testing standards. Current tests include Static Decay FTM 4046, Surface Resistivity ASTM-D-257, NFPA 99-Static Decay Test (formerly NFPA 56A) and Surface Resistance of 50% RH ESD 2.1.”

Static dissipation will become increasingly important as nanoparticles, nanotechnology and further miniaturization become more common.

Testing

Fabric must be tested for weight, pore size, moisture-vapor transmission rate, tensile strength and surface resistivity. The construction of the garment is evaluated for entraining particles and durability. Validation of a reusable garment system will require an audit of the cleanroom laundry-service provider.

In 2003, the IEST published the recommended practices for garments, IEST-RP-CC003.3, Garment Considerations for Cleanrooms and Other Controlled Environments. This 48-page document, replacing the globally accepted CC003.2 version, studies fabric, cleaning, maintenance and garment configuration, selection and specification for various cleanroom applications in aseptic and nonaseptic cleanrooms and other controlled environments. The new version has an expanded section on fabrics, material properties and testing, and the design and construction of the apparel. Processing considerations for the user and processor are outlined. Particle penetration testing guidelines including pore diameter testing of fabrics using a body box, and Helmke Drum testing and microbial penetration testing are included. Classification tables describe cleanliness categories in particle size ranges of 0.3 to 0.5 micron.

Testing a garment for particulate follows industry standards and procedures set up by ISO, American Association of Textile Colorists and Chemists (AATCC), the Association for the Advancement of Medical Instrumentation (AAMI), and other organizations. ASTM F51-68 (American Society for Testing and Materials) is a standard method for sizing and counting particulate contamination in the size range of 5 microns or larger in and on cleanroom garments. This test is simple but time-consuming and less reproducible. A section of the garment is placed over gauze screen, one square foot in area, and is vacuumed using a filter paper holder. This testing method does not work for membrane garments, however. The Helmke Drum places garments in a rotating drum with an automatic particle counter that determines the particle density level. The Helmke Tumble test evaluates particles at 0.3 micron and larger. More recently, the Gelbo-flex test is used. Many labs provide these types of testing, as do many of the national laundry services. Third-party quality validation will involve ISO 9001:2000, ISO 13485 for medical device manufacturers and EC Certification for products sold in the European Union.

At the Royal Institute of Technology (KTH) in Sweden, a modified dispersal chamber has been used to study the protective efficacy of cleanroom clothing.2 No significant performance difference was seen between disposable clothing and the two sets of reusable clothing that were washed and sterilized once. The use of special cleanroom undergarments enhanced the filtration efficacy of both particles and colony-forming units. However, the number of colony-forming units generated did increase as the number of washing and sterilization cycles increased.

Comfort

Many factors contribute to a cleanroom worker’s perception of comfort. Is the garment too hot or too cool? Is it too tight-fitting or, as was described in one survey, too loose, causing the workers to trip and fall.

The stiffness of the garment or-to use the industry term, the “hand” or general feel of the garment-is an important factor. Moisture vapor transmission rate (MVTR), the rate at which moisture is transmitted through the garment, is often used as a measure of comfort. MVTR testing models the ability of a garment to move perspiration away from the wearer and cool the body. MVTR is measured in units of grams/meters squared/24 hours. As a practical example, a vinyl raincoat has little moisture-vapor transmission, making the wearer very uncomfortable.

For the greatest user efficiency of reusable cleanroom garments, the correct design, size and fabric must be considered. Protective performance can be limited by penetration through fabrics, seams and fasteners, and by leakage between the garment and the body at seals, especially at the neck or wrists. Penetration through seal gaps can permit unhindered passage of large particles that would be unable to pass through the garment fabric.

Construction and durability

According to Bengt Ljungqvist, professor and head of the department of Civil and Architectural Engineering at KTH, the properties of the fabrics used for cleanroom clothing can be assessed by measuring air permeability, particle retention and pore size. The effectiveness of cleanroom clothing will deteriorate with factors such as aging, wear, washing, drying and sterilizing. Fabric strength and durability can be a factor of garment weight. Tongue Tear and Grab Tensile tests provide measurements of these qualities.

According to Robin Howie, the air permeability of seams and fasteners in many garments is much greater than that of the fabrics. Consequently, although the area of seam and fastener is typically less than 1 percent of the total area of the garment, the total flow of contaminated air through seams and fasteners can be much greater than through the fabric. Seam construction and components are part of the IEST recommended practice.

Seams must be bound using continuous polyester thread. No less than 12 stitches per inch should be used when sewing the garment. The seams should also be enclosed to ensure that no particles escape. Some designs, like GORE-TEX® cleanroom garments, are available with sealed seams that eliminate particle transmission through needle holes. Zippers should be made without coatings, which may break down, creating contamination. The pharmaceutical industry uses stainless-steel zippers, while the semiconductor industry, because of the risk-averse nature of loose metal contaminants, uses plastic zippers. If studs are used in the garment, they should be noncoated stainless steel or plastic. Some garment manufacturers purchase cuffs for the garments as a specialty knitted fabric. Other garments do not have knitted cuffs but rather snap or elastic closures made from the same material as the garment itself. Knitted cuffs may present the potential for breakdown and produce particles during the wash process, states Bill Steacker of Green Mountain Knitting (Milton, Vt.; www.greenmountainknitting.com). The firm currently has little demand for knitted cuffs used for cleanroom garments, though antistatic cuffs still are purchased. Others whom we interviewed commented that they purchase knit cuffs from suppliers with laboratory data indicating there is no breakdown, either mechanically or electrically, after years of use.

References

 

  1. ANSI/ESD S20.20-1999: Protection of Electrical and Electronic Parts, Assemblies and Equipment (Excluding Electrically Initiated Explosive Devices), ESD Association, 1999.
  2. Ljungqvist, Bengt and Berit Reinmuller. “Aseptic Production, Gowning Systems, and Airborne Contaminants,” Pharmaceutical Technology, May 2005.

 

Robert McIlvaine is president and founder of the McIlvaine Company, Northfield, Ill. The company first published “Cleanrooms: World Markets” in 1984 and has since continued to publish market and technical information for the cleanroom industry.

Betty Tessien is the cleanroom publications editor for the McIlvaine Company.

Source: http://electroiq.com/blog/2006/02/reusable-cleanroom-garments-part-1/

Issues Regarding Clothing for Sterile Cleanrooms

ISSUES REGARDING CLOTHING FOR STERILE CLEANROOMS

 

The following comments are meant to stimulate discussion and not to provide final answers. In many cases there are claims made which need to be more thoroughly debated.  Links have been provided to hundreds of pages of analyses which are meant to support the claims. We will keep revising this overview to reflect the comments of those providing additional insights and counter views.

USER COMFORT AND HEALTH

Comfort

Protection against liquid spills

  • Verbal observation that in Europethis is a bigger consideration than in the U.S.
     

  • This is also a bigger concern in healthcare such as surgical suites. So there needs to be discussion among hospital and industry specialists

Protection against toxic products

  • Cytostatics example: Any work with cytostatics requires the effective protection of workers from the dangers of drugs, which can have various carcinogenic, mutagenic and reprotoxic impact. At the same time, it is important to protect the product against contamination from people. Workers must therefore be required to wear suitable protective clothing.. Cytostatics are used as drugs in cancer therapy (chemotherapy) to inhibit the multiplication of tumor cells and are also used increasingly to treat other diseases. However, their toxicity affects not only tumor cells but also healthy cells.

To prevent hazards to staff while handling cytostatics, a range of suitable precautions must be taken. Both clean cleanroom clothing and chemical protective clothing need to meet the same basic criteria for use in a cleanroom: the material must be low-linting, the design must be sufficiently tight, and the danger of collecting particles on the surface of the garment must be minimized. To be suitable for dealing with cytostatics, such clothing must also be comfortable to wear, it must have good electrostatic discharge efficiency and sterilization must be possible. As well as providing product protection, Tyvek® and Tychem® protective clothing and accessories also meet the requirements on chemical protective clothing in Category III and thus personal protection.

Wicking properties for perspiration

Garment stiffness

  • Frequently voiced complaint about Tyvek.
     

  • On the other hand it is lighter and this may offset stiffness tendency.

GARMENT DONNING

Conclusions of Kimberly Clark survey

  • The sterile cleanroom gowning process takes between 5 and 10 minutes for the vast majority of cleanroom operators.
  • Almost one-third of cleanroom operators indicate that cleanroom coveralls are the most difficult part of the six-step gowning process, and that donning coveralls takes an average of 30 percent of the entire gowning process time.
  • Cleanroom operators are disposing of an average of 10 percent of their sterile cleanroom garments every week due to exterior contamination during the gowning process.
  • Most new cleanroom operators need 30 hours of initial training on cGMP donning procedures before they are allowed in the cleanroom itself, and an average of six hours of ongoing training each week.
  • Built-in snaps which gather up legs and arms to lower the risk of the garment touching the floor, then automatically release as the garment is put on.
  • Aninside-out fold pattern  presents the inside of the garment as the package is opened, reducing the risk of touching and contaminating the outside of the apparel.
  • A highly visible blue line along the inside of the garment  signals the proper place to grasp while gowning, helping workers avoid touching the exterior of the garment.
  • Thumb loops help keep the garment from riding up the arm and help to maintain the glove/garment interface.

http://www.mcilvainecompany.com/Decision_Tree/subscriber/articles/Donning-by-Design.htm

Comments about the survey

  • Thumb loop was developed a number of years ago.

GARMENT LIFE

Deterioration of Tyvek with gamma sterilization

  • It is a function of intensity.
     

  • Deterioration is apparent by the second or third time the garment is sterilized.

Deterioration of reusable garments with processing

  • See KTH study under laundering below

PRODUCT STERILITY

Anti microbials

  • For the first trial which utilized a permanent finish of propyldimethyloctadecyl ammonium, the treated and non-treated garments yielded similar CFU counts at the soil stage, but the treated garments had significantly lower CFU counts after the final wash cycle. For the second trial which utilized organ functional silanes, the data yielded little difference in CFU counts from the treated garments to un-treated control group for the third trial which utilized oxygenated bleach products, the data gathered yielded little difference in CFU counts from the treated garments to un-treated control group. The treated garments however, showed a very consistent and low, single digit CFU reading, which was very encouraging. The most intriguing result from all three trials was the performance of the control sets of garments. With a few exceptions during the second trial, they performed well, with counts well within an acceptable range, lending credence to the value of a stringent wash and handling processProtection or Hype

Undergarments

  • In sterile environments, Richard Bryant of Nitritex (Suffolk, UK) states that it’s recommended that cleanroom undergarments be used as an alternative to street clothes. These should be manufactured using nonlinting polyester barrier fabrics. The use of nonlinting polyester undergarments with a good coverall containment system will lower the number of particles carried into the cleanroom environment. Reusable Cleanroom Garments, Part 1, February 2006.

    Knitted cuffs-concern of particulate

Seam techniques to avoid particle passage

  • Special kinds of seam techniques are used for sewing these garments in order to avoid the passage of particles inside or outside the apparel. There are particularly three kinds of seams: • Interlocked stitching: Two pieces of garments are joined together with an interlocking stitching technique. • Double needle stitching: Two pieces are interlocked and then sewed with a double needle. • Layer bound stitching: A third layer of garment is put over the seam and stitched to ensure extra protection Seam Technique for Disposable Apparel

Laundering

  • A dispersal chamber at KTH has been used to determine that relative to microbiological contamination no significant difference was seen between disposable and reusable clothing washed and sterilized once. But there was a big increase in particles escaping after 25 wash and sterilization cycles. Aseptic Production, Gowning Systems and Airborne Contaminants 
     

  • Most cleanroom garment laundries have validated their processes for at least 100 launder cycles for the cleanroom garments they supply to the cleanroom industry. However, Jan Eudy recommend an objective testing of the cleanroom garment and fabric as well as establishing the efficacy of particle entrapment, the lack of particle shedding, and ESD efficacy as the criteria for replacement. When Should Cleanroom Garments Be Replaced? 
     

  • InterWEBview with Jan Eudy of Cintas asserts that there is a big difference between a good laundry and a mediocre one in terms of garment deterioration per wash cycle. Reusable Garments InerWEBview with Jan Eudy of Cintas, February 2011

Q &A procedures: How reliable:

CCMG requirements more stringent now than before

Hospital pharmacies have special requirements

Packaging

  • Packagingmust first assure that the product is sterile at the time it is sealed. It must provide for maintenance of sterility prior to opening. It must be user friendly to prevent contamination upon opening.
  • Can reusable garment consistently meet these criteria. The single use garment proponents say that laundries are dealing with smaller numbers and cannot be sufficiently well organized to prevent sterility lapses. In response we need input from those laundries that are so organized.
  • A unique process to package the new garments for sterility assurance. The technology uses a vacuum seal process to allow the breathable SMS fabric to be sterilized with Gamma irradiation. The unique look and irradiation indicators on each package help to confirm irradiation and sterility. http://www.mcilvainecompany.com/Decision_Tree/subscriber/articles/Donning-by-Design.htm
  • To what extent is the packaging design requirement affected by the gowning procedures and by the physical aspects such as the gowning area and pass thru?

GARMENT DESIGN

Sizing

Shapes

 

SINGLE USE VS. REUSABLEFOR STERILE ENVIRONMENTS

The greater the number of changes the more greater the attractiveness ofreusables

  • In sterile environments fabric that is resistant to multiple sterilization cycles must be used in the manufacture of the garments. Garment changes – cleanrooms that require 20 garment changes per week should be looking to use reusable launderable garments. Getting the Best Garment Service

Variation by cleanroom class

  • Disposable garments are a viable option for some users and applications. Horton says disposables make sense in many ISO Class 6 operations and those that are not conducive to garment cleaning, such as nuclear, some types of food processing, and some pharmaceutical applications. Disposable garments also might make sense for companies that have low gown usage requirements, and they are recommended in biohazardous critical environments (BSL-2, -3, and -4 cleanrooms) and heavy soil applications such as preventive or corrective maintenance of equipment in the cleanroom, according to Eudy The Well Dressed Cleanroom

Comfort comparison

  • Research shows that single use garments, which are more comfortable, easier to don, and minimize contamination are highly valued in the pharmaceutical industry. Cleanroom Clothing InterWEBview™ with Damon Larkin of Kimberly-Clark
     

  • Several interviewees contest this claim and say thatSMS and Tyvek and similar garments are less comfortable due to heat. Reusable Garments InerWEBview with Jan Eudy of Cintas, February 2011

  • What is hot to a heavier person may seem comfortable to a thin person. In an office setting with a constant temperature of 70 degrees F. Some people will complain of heat and others of cold.
     

  • Two variables are the physical make up of the individual andsecondly the conditions. The location in the cleanroom can make a difference.  The amount of physical activity is another.

Sustainability and Greenhouse Gases

Garment Particle Shedding (as opposed to the people inside the garment)

  • Helmke drum tests are unreliable.  Place a garment one way in the drum and get one result. Place it another way and get a different result (Moschner-Dastex).
     

  • More analysis needs to be done of garment particle shedding.

 

Fabric Choices Single Use

SMS

  • SMS (Spunbond Meltblown Spunbond) material that provides a cloth-like feel and is 25 times more breathable than TYVEKhttp://www.mcilvainecompany.com/Decision_Tree/subscriber/articles/Donning-by-Design.htm
     

  • For the past 40+ years, disposable cleanroom suits have been made from flash-spun polyethylene fabric. According to industry analysts, flash-spun polyethylene provides filtration efficiency for sub-micron sized particles and microorganisms and is suitable for light splash protection from non-hazardous liquids. Disposable suits also can be made from spunbond meltblown- spunbond (SMS) fabric, which has outer layers of spunbond polypropylene for strength and cloth-like comfort, with middle layers composed of a matrix of microfibers, which creates a torturous path for fine particles and liquids. the Human Element

Tyvek

  • Tyvek nonwoven material has been upgraded over the years and has proven to be a good performer in Class 100 (ISO Class 5) to Class 100,000 (ISO Class 8) environments, depending on garment processing and packaging. Free-fiber generation at wear points, however, is a disadvantage of this material.. It’s a breathable fabric that provides filtration efficiency for submicron-sized particles and microorganisms, and it’s suitable for light splash protection from non-hazardous liquids. Unlike film laminates, the protective properties of Tyvek are an inherent feature of the material and cannot be abraded or scratched off. Disposable Cleanroom Garment Use and Markets, December 2005. 
     

  • The above claim relative to the free fiber generation at wear points was reported second hand and needs further analysis.

  • Material degradation becomes a factor for multiple wear garments. The desired Sterility Assurance Level( SAL) is 10(6) insuring a one in one million probability of a garment being nonsterile. This requires more radiation which reduces the life of multi wear garments. The supply chain for multiple use garments is complicated and generally requires contracts with processors of 1 to 5 years. Supply chain for single use garments is less complicated There are two general approaches that a pharmaceutical company can use to assure the quality of incoming garments. • Use internal personnel to monitor and periodically audit • Third party verification of supplier quality system Third part verification requires a certification system (e.g. two ISO standards and or EC Certification) Comfort is another factor . the non woven Tyvek used in single use garments is lighter than woven materials used in multiwear garments. Tyvek is comparable in air permeability but is stiffer. Comfort is typically quantified through air permeability water vapor transmission rates and material stiffness. Apparel System Selection for Pharmaceutical Cleanrooms

Fabric Choices - Reusable

Fabric Options

  • According to John Smith of Precision Fabrics Group (PFG), in the US market, most of the fabrics sold are plain weaves, whereas in Europe, a much higher percentage of the fabrics are twill weaves. “Since the fabrics have to perform the same function of particle filtration, it seems that both can do so if they are properly constructed,” Smith continues, “. The advantage that the twill weaves have is that the hand is more supple than a plain weave, although the plain weaves become more supple after laundering. The disadvantage is the higher fabric weight and, therefore, garment weight, and potential latent release of particles if the laundering is not done properly. Reusable Cleanroom Garments ,Part 2, March 2006. 
     

  • Burlington C3® is engineered to meet a Class 10 cleanroom's rigid demands for the microelectronics industry. The fabric is designed to guard the product against airborne particles, static dissipative charges, bacteria, and lint. It is made from a dense plain weave 100 percent multifilament polyester yarn with a microengineered carbon fiber inter-woven into a grid pattern.

  • Stern & Sterns CHEMSTAT 909 and 909A are two antistatic fabrics with a patented conductive yarn that is an extruded copolymer of polyester and carbon that is impervious to industrial laundering in excess of 300 washings. CHEMSTAT 909A is a tighter version of the CHEMSTAT 909 material for use in Class-10 cleanrooms. Both are 100 percent DACRON polyester fabrics employing the patented raised grid conductive fiber for static dissipation. 
     

  • DuPont's 100% Dacron polyester yarn is woven into both taffeta and herringbone weaves. Taffeta fabric is constructed in a plain weave while herringbone is a heavier broken-twill weave that produces a balanced zigzag effect. Both serve in many cleanroom and peripheral area applications as an effective barrier for airborne particles and bacteria filtration. 100% Dacron polyester: Taffeta 2.58 oz/ sq. yd.- Herringbone 4.3 oz/sq yd Excellent resistance to acids and alkalis  Extremely limited tinting·  High resistance to sagging.
     

  • INTEGRITY 2000® Precision Fabrics INTEGRITY 2000"is a densely woven filament DACRON polyester grid fabric designed to meet the quality and performance standards demanded by the protective apparel industry. This product is highly fluid repellent and also contains a durable antimicrobial compound.
     

  • Teijinselguard Selguard II® is a highly functional Class 100 cleanroom fabric which offers both excellent particulate control and antistatic performance without compromising employee comfort. This non-linting fabric is a continuous filament, 100 percent polyester twill with electrically conductive fibers sleeved in polyester and integrally woven into a grid design.

 Source: http://www.mcilvainecompany.com/Decision_Tree/subscriber/Tree/DescriptionTextLinks/Issues%20regarding%20clothing%20for%20sterile%20cleanrooms.htm

Cleanroom Garments for Critical Manufacturing

Critical Manufacturing

Critical Manufacturing encompasses a variety of industries including medical device, automotive paint spray, injection molding, avionics, medical equipment, pharmaceutical and a number of other related industries.

Most companies have cleanrooms that operate to ISO 14644 requirements, while others may rely upon sub-vendors with cleanrooms for assembly and packaging. There are a number of articles on cleanrooms and controlled environments, but the primary purpose of any ISO certified room is to maintain airborne particulates to a specified limit, generally defined as the number of particles per cubic meter at a specified particle size. 

Cleanrooms are classified from ISO 3 to ISO 8, with ISO 3 being comparable to the old Federal Standard 209E Class 1 cleanroom. The GSA cancelled the FED STD 209E in 2001, but many still refer to their rooms using the old standard.

The most common source of contamination originates from employees. Unless the room is controlled, and unless workers are properly gowned to the room’s specification, hair, skin flakes, saliva, lotions, make-up, perfumes, coughing/sneezing, and perspiration can create the majority of airborne contamination problems in cleanrooms. 
 

Source: http://epwhse.net/mfg.html

Cleanroom Garments for Food Manufacturers

Food Processing

Though commonly found in pharmaceutical and semiconductor applications, cleanrooms are increasingly being used to control and avoid contamination in many food manufacturing processes. Used primarily to control airborne particulate and improve product quality, cleanrooms and cleanroom garments protect not only the environment, but also your employees.

In seeking to control airborne contamination, commonly referred to as particulate, and the spread of bacteria, food manufacturers are turning to cleanrooms and the use of cleanroom garments. Your requirements may vary by the products you produce, and in defining what problems and specifications you need to meet. 

Personal cleanliness must be one of the first priorities in food processing operations.

Source: http://epwhse.net/food.html

ESD Cleanroom Garments for Semiconductor and Microelectronics

Semiconductor & Microelectronics

Electrostatic discharge is a major cause of product failure, and can endanger employee safety and lead to costly delays in production. 

While the industry continues to evolve and change, today more than ever controlling electrostatic discharge (ESD) is achieved in part with the proper selection of cleanroom garments. 

One of the major causes of static electricity and particulate levels in cleanrooms is your employees.It’s been found that people can shed the outermost layer of skin cells every day, which can contribute to increased particulate levels and airborne bacteria. Your company’s selection and use of cleanroom garments is critical to controlling these occurrences. That’s why the use and application of specially designed cleanroom garments is critical. The most common garments are ones that can be connected to ground points and garments that establish resistance from one point to another point on the garment. 

 

Source: http://epwhse.net/esd.html

Cleanroom garment systems for Pharmaceutical and Medical Device applications

Pharmaceutical and Medical Device

The introduction of human contamination into manufacturing processes utilizing cleanrooms and cleanroom garments is one the greatest concern for companies in the Pharmaceutical and Medical Device industries. The proper selection of cleanroom garments is critical in preventing contaminants carried by employees from entering into the cleanroom. 

Managing the cleanroom garment system for Pharmaceutical and Medical Device cleanroom applications can be complicated due to the exacting requirements and production challenges of your industry.

The first step is to identify your production requirements and the ISO classification of the cleanroom to ISO standard 14644-1. In most cases this classification will determine your proper gowning. Here are some recommendations based upon the rooms classification.

ISO Class 4: (Class 10)
-    Disposable Bouffant/Hair Cover
-    Hood
-    Facial shield or goggles
-    Beard Cover(If necessary)
-    Face Mask
-    Coverall
-    Gloves 
-    Disposable shoe covers
-    Boots


ISO Class 5: (Class 100)
-    Hair Cover
-    Hood
-    Beard Cover (If necessary)
-    Face Mask
-    Coverall
-    Disposable shoe covers
-    Boots
-    Gloves


ISO Class 6: (Class 1000)
-    Hair Cover/Bouffant
-    Beard Cover(If necessary)
-    Coverall 
-    Shoe Covers/Boots
-    Gloves


ISO Class 7: (Class 10,000)
-    Bouffant
-    Beard Cover(If necessary)
-    Frock
-    Shoe Covers

Source: http://epwhse.net/pharma.html

Getting the best cleanroom garment service

As every cleanroom operator is aware, among the most important facets of cleanroom management are ensuring the prevention of contamination and the provision of sufficient comfortable clothing to ensure that operations can continue uninterrupted.

Contamination – considered anything that has an effect on quality or performance of the products being manufactured or processed – can take the form of particulates, bio-pollutants, chemical cross-contamination or even electrostatic discharges (ESD), which individually or collectively have a detrimental effect on product or process performance.

The contaminants concerned are normally invisible to the human eye and can be as small as 0.1 micrometres (µm), which makes their control and elimination a huge challenge. A key to that control is an understanding of where the particles come from. Up to 80% of all particulates are the human detritus that is shed by the operatives working in the cleanroom.

Typical particle generation from everyday activities

Each of us sheds our outer layer of skin every week in the form of loose particles (about 4–5µm) or groups of cells (typically 25–30µm). Once present in the environment these particles are broken up and ground down by human activity or other mechanical abrasion into the very fine dust particles that are so easily dispersed into the atmosphere. As these particles are human derivatives there is a high probability that some will contain chemicals and bio-residues, such as bacteria.

No amount of scrubbing and cleaning can prevent cleanroom operatives from shedding particulates, so it is impossible to eliminate their source. This means that we have to accept that containment of these particulates is essential to prevent them from being released into the cleanroom environment. The key to this control is the use of high-specification cleanroom clothing.

When deciding on the management of cleanroom clothing the cleanroom operator has three options to choose from: single use disposable garments; reusable launderable garments; or a combination of the two. The influencing factors are: the garment system required to achieve the desired level of containment; the number of changes of garb required by each operative per day; the number of occasional visitors into the controlled area; and the level of support and service provided by the cleanroom laundry.

As a rule of thumb, once the number of garment changes per week reaches 20, the best strategy for the cleanroom operator is to opt for reusable launderable garments, using an independent cleanroom laundry to supply, maintain, clean, pack and manage the necessary garment stock.

Garments

Typically, the following factors will need to be considered when choosing the type of garments that are appropriate for use in the cleanroom:

  • The class of cleanroom – the higher the classification, the greater the need for full body coverage. For instance, in ISO Class 51, or European GMP2 Grade A or B cleanrooms it is essential to wear coveralls, hoods, boots, facemasks and gloves.
  • Type of cleanroom – in sterile environments fabric that is resistant to multiple sterilisation cycles must be used in the manufacture of the garments.

     

  • Static electricity – this causes a variety of problems in cleanrooms. The spark from an electrostatic discharge can damage products (e.g. in electronic component manufacture) or can start a conflagration in explosive atmospheres. Just as house dust is attracted by and sticks to the television screen because of static electricity, so cleanroom particulates and bacteria are attracted to cleanroom garments that hold a static charge. For these reasons it is important that garments are made from material that is static dissipative with a surface resistance that is typically in the range of 106–108 Ohms.
  • Garment changes – cleanrooms that require 20 garment changes per week should be looking to use reusable launderable garments.
  • Compatibility – it is important that the garments integrate seamlessly with other items such as gloves, masks and footwear.
  • Visitors – if there is a large number of visitors to the cleanroom on a regular basis and launderable garments are in use then holding a small stock in a range of common sizes is the best option. If the number of visitors is minimal disposable garments are probably the most economic option.

Garment construction

If the purpose of launderable garments is to contain contamination from the wearer then the garments themselves must not be a source of particulates. The construction of the garments and the materials used must ensure that this goal is achieved. There must be no raw fabric edges in evidence anywhere in the garment, so all seams should be of either French, bound or lapped construction. As well as containing the particulates from the material edges these seam construction methods prevent the free passage of air (and hence contamination) from the inside of the garment into the cleanroom.

At the planning stage it is vital to consider any additional features, such as pen loops and studded cuffs, that will affect the overall performance of the garments. Features, such as pockets, pleats and additional seams, should be avoided as they create entrapment areas for unwanted contamination.

The fabrics used must be non-linting (usually close woven polyester), comfortable to wear and anti static (or more correctly, static dissipative). Antistatic fabrics are usually recognisable by a grid or stripe pattern that is woven into the cloth using electrically conductive thread. The garments should also be carefully designed so that they are comfortable to wear when donned correctly, giving operatives no reasons for not fastening collars and cuffs correctly.

There are two methods of testing garments for particulate emission. The first uses a Helmke Drum3, where the garments are put into a rotating stainless steel drum and an airborne particle counter measures the number of particles over 0.3µm/ft3.

In the second,4 air samples are drawn through a filter on certain parts of the garment to determine the quantity of particles and fibres in and on the garment.

When deciding on both garment design and fabrics, consideration should be given to the anticipated processing that the garments will encounter during their lifecycle. Beyond laundering, these are primarily sterilisation processes, such as irradiation or autoclaving, which will have a detrimental effect on garment lifespan.

Allowance should also be made for wearers carrying out tasks exposed to greater wear or staining. Their garments should be ring-fenced from stock in general circulation to avoid cross-contamination and deterioration of the stock.

Selecting a laundry

The ideal cleanroom laundry will have the capability to provide a complete and integrated service from the identification of garment needs through to the availability of ready to wear stock at the cleanroom site. It will build its support structure around the client’s requirements rather than the other way round. The ideal laundry will have the infrastructure, procedures, flexibility and understanding to ensure that clients can forget about their garment needs once a contract has been signed.

Laundries should be built and maintained as ISO Class 5 cleanrooms

The cleanroom laundry must itself be built and maintained as an ISO Class 5 cleanroom using ultra-pure deionised water to wash the garments, with line clearances and planned cleandowns between batches. The line clearances are used before garments are moved from one area to another to avoid any possibility of garment mix up.

In addition, cleandowns involve the swabbing down of surfaces and areas to prevent contamination. Regular particulate monitoring must be carried out in the laundry and independent audits of the room and water supplies should be conducted frequently.

Cleandowns should involve the swabbing of surfaces and areas

Garment identification and tracking is essential to ensure receipt and delivery reconciliation. This provides a cradle to grave history of each item in circulation as well as management information relating to garment usage and other key data to help the partner to adapt to changes in requirements.

Logistics and garment replacement are key elements of the overall service. If items are not collected and delivered as per the agreed schedule or deliveries are short, it severely impacts the seamless operations of the cleanroom.

Finally, there is the issue of overall customer service. This can be construed as a myriad of different elements. Clear service goals and metrics should be documented as part of a Service Level Agreement (SLA) so that both supplier and customer have a clear understanding of how the contract will operate throughout its term. As part of the SLA it is important for supplier and client to be clear how and when garments are to be repaired in terms of quality and appearance. For example, some companies have frequent client visitors to the cleanroom and do not want garments with patches undermining their corporate image.

Each party must have a clear understanding of the point at which it becomes uneconomic and unrealistic to repair a garment and have it replaced. No garments should be inserted into circulation without prior consent from the customer. The supplier’s reputation, industry knowledge and experience in the cleanroom environment provide additional security for any cleanroom operator seeking a new laundry provider.

Proper management of cleanroom garments and ensuring that users adhere to the correct protocols are essential to ensure garment life is maximised and wastage reduced. Detailed reports on garment lifecycle, repairs and user compliance should be available to provide information for efficient cleanroom operation.

Broad service options

In summary, to maintain cleanroom operational efficiency, it is vital that the correct garments are selected based on the points discussed, the garments are cleaned and maintained to the highest possible controlled manner and that there is good integration between the garments and consumables, such as gloves and masks.

The broad range of garment requirements and service options means that contracts can become complex. It is, therefore, important that the cleanroom laundry is flexible in its approach, giving options to cleanroom operators that suit their needs, and this should include options such as:

  • Full service – all-inclusive package

  • Split rental – separate charges for garments and laundry processing

  • Process and maintain – charged per item

  • Lease to own – no residual charges at the end of contract.

References

1. ISO 14644-1: 1999, Cleanrooms and associated controlled environments. Classification of air cleanliness, International Standards Organisation

2. Rules and Guidance for Pharmaceutical Manufacturers and Distributors, Medicines and Healthcare products Regulatory Agency

3. IEST-RP-CC003.3, Garment Systems Considerations for Cleanrooms and Other Controlled Environments, Institute of Environmental Sciences and Technology

4. ASTM F51-00 (2007), Standard Test Method for Sizing and Counting Particulate Contaminant In and On Clean Room

Source: http://www.cleanroomtechnology.com/technic...