Cleanroom Contamination Sources & Prevention
Cleanrooms provide a controlled environment for the successful operation of highly sensitive productive applications. Some of these applications include:
- Aerospace production
- Pharmaceutical production
- Nutraceutical production
- Medical device manufacturing
Different clean room standards require various restrictions on airborne particle concentration and levels of contamination. These standards require constant maintenance from powerful HEPA filtration systems, strict clothing requirements, rigorous cleaning regiments, and more. Listed below are several sources of contamination and bacteria, as well as several solutions to reduce their numbers.
- Facility: Contamination can come from anywhere in the facility: dirt, debris, dust, shavings, floors, walls, and ceilings. Particles can come from paint (and various other coatings) and construction materials like sheetrock or wood. Debris can come from air conditioning systems, and spills, leaks, and room vapors can contribute to contamination.
- Cleanroom equipment and supplies: Contamination can also come from clean room equipment and supplies. Friction and wear from equipment use can result in particles released as well as lubricants and emissions from motorized equipment can create contaminates. Vibrating equipment could give off particles, and cleaning materials can shed all sorts of particles and residue, such as brooms, mops, and dusters.
- Staff: Skin shedding accounts for a large proportion of particulates released into a given environment. Oils from skin, hair, and spittle can also contaminate a cleanroom environment. Cosmetics and perfume should be avoided when working in the cleanroom because of their potential contamination risk. Additionally some clothing can shed contaminants through lint and various fibers.
- Environment and fluids: Contamination can come from various environmental effects and substances such as fluids. Particles floating in the air can reach cleanroom environments. Microorganisms such as viruses, bacteria, and microbes can also be a source of contamination. Bacteria can develop in warm, moist conditions, and moisture can sometimes be considered a source of contamination in certain contexts. Floor finishes, coatings, or chemical cleaning products can contribute to contamination, plasticizers and deionized water can contaminate as well.
- Products: Finally, contamination can be generated from the products resulting from the applications. For example, silicon chips can shed particles, and contamination can also come from quartz flakes, aluminum, and other cleanroom debris.
Cleanrooms are specifically designed to reduce or even eliminate many of the sources of contamination listed above. That said, contaminants can flourish in regular, unregulated environments; unfiltered air can contain millions of particulates at any time. Certain environment temperatures (such as warmer temperatures) can encourage microbial growth such as viruses, fungi, spores, and bacteria.
People are also a substantial source of contamination. Uncovered hair and skin can shed substantial amounts of particles and oils. Standing, we can give off about 100,000 particles a minute, and walking 2 mph, that number can jump up to 5,000,000!
Strategies to Minimize Contamination
HEPA filters are used to filter particles as small as 0.3 microns with a 99.99% minimum particle-collective efficiency. Oftentimes, a laminar airflow pattern is used where air flows down from the ceiling via fans, “scrubs” the floor of particulates and carries them to the filters. Additionally, there can be other secondary filtration systems used to remove particles from gases and liquids that can complement the HEPA filters and make filtration more effective.
Cleanroom architecture is specifically designed to allow the easy passage of air over surfaces, reducing areas where carried particulates can collect and sit. Recessed lighting and vents, coved floors, covered light switches, and specialized furniture are all examples of clean room features used to reduce air turbulence and prevent the build up of contaminants.
To keep staff from tracking contaminants in from the outside, strict dress code and procedure is enforced. Clean room staff should wear special gowns or jumpsuits which cover their day clothes. Additional protective clothing may include masks, goggles, gloves, and hoods to cover their hair. Clean room staff are often required to wear special shoe coverings which they usually have to clean with scrubbers before entering the cleanroom. Many personal cosmetics are often prohibited, and clean room staff often pass through air showers before entering clean rooms.
If any contaminants are missed after the above precautions, rigorous manual cleaning regiments are typically used to keep cleanrooms contaminant-free. Special cleanroom-friendly solvents, brooms, and other cleaning materials are used to keep surfaces clean and contaminant-free. Cleanroom equipment is carefully screened, and specialized papers, wipers, and writing utensils are used. These specialized products are important because they don’t shed particulates and fibers like traditional supplies do. Continuous cleanroom testing is often conducted to measure particle levels, air flow, humidity, temperature, and surface cleanliness. Testing ensures that cleanrooms are operating at the highest levels of cleanliness, and the room is functioning properly.
Contamination can come from many sources under various environmental conditions, including particles, fluids, and microbes are considered contaminants. These contaminants can pose a danger to many different types of sensitive applications. However, if the proper regulations and regiments are put into place, a cleanroom can be kept free of harmful contaminants.