Cleanroom Dangers

Any material, substance, particle, chemical, or other undesirable substance that is unwanted that can taint, pollute, defile, make impure or unclean, or adversely effect the process or product. Contamination can take many forms such as: particulate, chemicals (including gases), electro-static discharge, viables ( bacteria, molds, etc..), and other forms.

Particles are measured in microns. If you were to slice a 1-inch cube into 25,400 equal pieces, each slice would be 1 micron thick. (So thin that you could not see it.)

Since cleanroom facilities contain invisible particles that can cause defects, we need to have a way to determine their sizes and possible sources. These particles cannot be seen with the naked eye and yet may cause serious loss to our client and to their ability to manufacture devices without defects. We measure the amount of particles in the air with a device known as a particle counter. This helps us to determine when to perform or restrict certain activities.

Typical Pollutant Sizes That Cause Down Time

Bacteria	.01 to 1.0 Microns
Dust	1.0 to 10 Microns
Mold	1.0 to 10 Microns
Hair	10 to 100 Microns
Pollen	10 to 100 Microns

Following are some common sources of contamination. This list in by no means exhaustive, but it gives you and idea of the types of things to be aware of when you are looking for the source of contamination.

Hair
Skin Flakes
Saliva
Make-Up
Lotions
Perfumes
Coughing / Sneezing
Excessive Movement
Perspiration
Wood
Paper
Cardboard
Tobacco Products

Gum, Cough Drops
Packing Materials
Duct Tape
Dirty Clothing
Chemicals
Caulks and Paints
Aerosols
Ions (Rust)
Permanent Markers
Non-Cleanroom pens
Smoke
Thinners /Solvents
Food and Drink

To combat the tremendous amount of particulate released by the human body, cleanroom personnel are asked to wear special garments that are restrictive and may be uncomfortable if the working conditions (temperature, humidity) are not carefully controlled.

People are dressed in booties, gloves, helmets, hoods and special facemasks that are not part of a normal experience. You are also asked to move slowly, to clean up dirt you cannot see, and to follow practices and procedures that may not immediately make sense.

The approach to cleanrooms is designed in steps so as to ensure that every effort has been made not to introduce contaminants into the cleanroom.

The Human Factor

"Humans are walking, breathing, waste pits from a microbiological perspective and there is no indication we are going to evolve into anything cleaner."

Human dust combined with sebum will tenaciously adhere to and contaminate surfaces, creating contamination problems that are simultaneously bacterial, chemical and particulate.

There is an additional complicating factor - normal human activity. Humans breathe, sneeze, cough, talk and move around. Body and breath temperatures cause heat turbulence in addition to air turbulence.

People slough off huge numbers of particles a half micron and larger and these are propelled around by air and body movement. Some examples of how many 0.5 micron and larger particles can be released by simple movement are shown below. Vast amounts of contamination need to be controlled in a cleanroom environment.

Activity

Particles Release

Seated	100,000 particles per minute
Moving 2 miles per hour	5 million particles per minute
Moving 3.5 miles per hour	7.5 million particles per minute
Moving 5 miles per hour	10 million particles per minute

Chart I. Contaminants, Sources and Potential Damage

Type	Source	Damage Potential
Metallics	Vacuum cleaner motor brushes, wear of A/C units, printer wear, raised floor and grid	Electrically conductive, magnetically attracted to micro-circuits
Carbonaceous	Automobile exhaust, tobacco smoke, printer toner, oxidized organic material, paper dust	Moisture absorbent, electrically conductive, combustible.
Synthetic Fibrous Particulate	Operator clothing, carpeted floor tiles	Low melting point, moisture absorbent, some type combustible , electrically conductive.
Cement Dust/Crystalline	Improper sealing or erosion of subfloor, ionization and crystallization of cleaning fluids, nicron wire heating elements, ion air purifiers.	May be propelled at high velocity into floor cooled components, clogged filters lead to overheating of disk media

Chart II: Equipment Manufacturers Statements on Contamination

IBM INSTALLATION MANUALPublication GC22-7072-1	"If your site is unusually dirty or has a chemical odor, you should be concerned. Dirt and corrosive gases can cause corrosion and possible equipment damage. The building floor should be sealed to prevent dusting of concrete."
AMDAHL PHYSICAL PLANNING MANUALPublication MM-108334-010	"Environmental conditions for the room environment must be maintained within the acceptable limits to prevent adverse impact on performance and reliability.Electronic equipment is sensitive to air contaminants such as ferrous metal slivers, dirt fibers, and concrete particulate from unsealed concrete.cement should be sealed to prevent the generation of particles."
UNISYS INSTALLATION MANUALPublication MA5227	"The quantity of dust in the air must no exceed 0.39 gram/1000m 3[0.03grain/1000ft3] maximum.The specifications for dust pollutants as per United states Federal Standard 209b.The primary floor must be poured concrete that has been sealed to provide dust and humidity control."
MMEMOREX ENGINEERING SPECIFICATIONSPublication 9885-4920	"In order to assure reliability operation of the HDA and its filter system, the size and type of airborne particles must be controlled.The computer room should meet or exceed Federal Standard 209E.The subfloor area must be cleaned and sealed prior to equipment installation".

Information Compiled From The Following Sources:

"The Seven Elements Every Manager Should Know About Computer Air Conditioning Liebert Corporation
"Halons And The Stratospheric Ozone Issues" EPA, Stephen O. Anderson, Ph.D.
"What You Don't See Can Hurt You" Infosystems Magazine
"The Slovenliness Factor" EC&M Magazine
"Indoor Air Quality" Engineered Systems Magazine
"Dust, The Unseen Downer!" Insite Magazine

Contact SET3 for a free walkthrough evaluation of your facility.

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