A Clean room is an enclosed area within a building with a controlled environment where products are manufactured, assembled or packaged. It is a room in which the concentration of airborne particles is controlled to specified limits. Clean rooms are classified according to the number and size of particles permitted per volume of air. Large numbers like “class 100” or “class 1000” refer to FED-STD-209E, and denote the number of particles of size 0.5 µm or larger permitted per cubic foot of air. Small numbers refer to ISO 14644-1 standards, which specify the decimal logarithm of the number of particles 0.1 µm or larger permitted per cubic meter of air. Both FS 209E and ISO 14644-1 assume log-log relationships between particle size and particle concentration. For that reason, there is no such thing as zero particle concentration. US FED STD 209E was officially cancelled by the General Services Administration of the US Department of Commerce November 29, 2001, but is still widely used.
Eliminating sub-micron airborne contamination in a clean room is really a process of control. People, process, facilities and equipment generate air born contaminants. They must be continually removed from the air. 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 employed and tightly controlled. Whenever possible the sources of these particles need to be controlled or eliminated. There is more to a clean room than air filters. Clean rooms 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. Once a Clean room is built it must be maintained and cleaned to the same high standards.
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. A partial list of contaminants is found below. Preventing these contaminants from entering the Clean room environment is the objective. Strict procedures should be followed whenever entering or cleaning a Clean room.
- Walls, floors and ceilings
- Paint and coatings
- Construction material (sheet rock, saw dust etc.)
- Air conditioning debris
- Room air and vapors
- Spills and leaks
- Skin flakes and oil
- Cosmetics and perfume
- Clothing debris (lint, fibers etc.)
- Friction and wear particles
- Lubricants and emissions
- Brooms, mops and dusters
- Particulates floating in air
- Bacteria, organics and moisture
- Floor finishes or coatings
- Cleaning chemicals
- Plasticizers (outgases)
- Deionized water
- Nylon, Polyester, Metal chips
- Quartz flakes
- Clean room debris
- Aluminum particles
Contaminate Control is addressed through:
Clean room Design – Clean rooms 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 parallel flow lines. This air flow is called laminar flow. The more restriction of air flow the more turbulence. Turbulence can cause particle movement.
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.
Filtration – In addition to the HEPA filters commonly used in Clean rooms, 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. Applications and procedures need to be written and agreed upon by Clean room management and contractors (if used).
Clean room Garments – The requirements for Clean room garments will vary from location to location. It is important to know the local garment requirements of the Clean room management. Gloves, face masks and head covers are standard in nearly every Clean room environment. Smocks are being used more and more. Jump suits are required in very clean environments.
Worker Behavior – There are both physical and psychological concerns when humans are present in clean rooms. Physical behavior like fast motion and horseplay, sneezing and coughing can increase contamination. The body’s regenerative processes: skin flakes, oils, perspiration and hair are sources of contamination. Psychological concerns like room temperature, humidity, claustrophobia, odors and workplace attitude are topics to be addressed in the use of a clean room.
Commodities – Care must be taken when selecting and using commodity items in clean rooms. Wipers, clean room paper and pencils and other supplies that service the clean room should be carefully screened and selected. Review of the local clean room requirements for approving and taking these items into the clean room are essential.
Cosmetics – Many cosmetics contain sodium, magnesium, silicon, calcium, potassium or iron. These chemicals can create damaging particles. Clean room managers may ban or restrict cosmetics in the clean room.
Measurement and Instruments – Some important measurements related to contamination control are particle count, air flow & velocity, humidity, temperature and surface cleanliness. Specific standards should be set, and instruments to measure these factors should be utilized
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 turboelectric charge. Special care may need to be taken to use ESD protective materials to prevent damage from ESD.
Some typical general regulations recommended as a minimum for the successful operation of a clean room are:
- No eating, smoking or gum chewing allowed inside the clean room.
- Only garments approved for the clean room should be worn when entering.
- All personal items such as keys, watches, rings, matches, lighters and cigarettes should be stored in the personal locker outside the gowning room.
- Valuable personal Items such as wallets may be permitted in the clean room provided they are NEVER removed from beneath the clean room garments.
- No cosmetics shall be worn in the clean rooms. 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.
- Use of paper or fabric towels are prohibited
- Approved ball point pens shall be the only writing tool used.
- Only approved clean room paper shall be allowed in the clean room.
- Gloves or finger cots should not be allowed to touch any item or surface that has not been thoroughly cleaned.
- 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.
- Solvent contact with the bare skin should be avoided. They can remove skin oils and increase skin flaking.
- Approved skin lotions or lanolin based soaps are sometimes allowed. These can reduce skin flaking.
- All tools, containers and fixtures used in the cleaning process should be cleaned to the same degree as the clean room surfaces. All of these items are a source of contamination.
- No tool should be allowed to rest on the surface of a bench or table. It should be placed on a clean room wiper.
- Only clean room approved wipers are allowed to be used. The wipers must be approved for the Class of clean room.
- All equipment, materials and containers introduced into a sterile facility must be subjected to stringent sterilization prior to entrance.
- No one who is physically ill, especially with respiratory or stomach disorders, may enter a sterile room. This is a good practice in any clean room environment.